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1: Tubes Asylum, RE: Tube health judging by Maximatcher ll readings (0.00)
Posted by Tom Bavis on 2024-03-21, 11:26:15 (98.3.112.80)
Transconductance generally falls off with use, so it is an indication of condition. As transconductance drops, distortion may increase. Peak emission is what determines maxim power output capability - .......
2: Tubes Asylum, RE: Who made this Telefunken labeled 12AX7? (0.00)
Posted by Tom Bavis on 2024-03-04, 08:27:00 (98.3.112.80)
Half circle with a dot is code for EI. .......
3: Tube DIY Asylum, RE: B&K 667 (0.00)
Posted by Tom Bavis on 2024-02-04, 11:51:45 (98.3.112.80)
Looks almost like new. Just leave the transformer leads alone. Caps I see are film - should last near forever, plus two electrolytics. One looks like it might have been replaced - check solder joints. .......
4: Tube DIY Asylum, RE: "Series" resistor needed for CCS -) glow tube? (0.00)
Posted by Tom Bavis on 2023-12-08, 13:37:10 (98.3.112.80)
You might want a resistor to limit dissipation in the CCS. But not so much that it drops out at low line. .......
5: Tubes Asylum, RE: 5U4G testing... (0.00)
Posted by Tom Bavis on 2023-12-08, 13:29:54 (98.3.112.80)
The Knight is as good as any tester for rectifiers. A few extra volts of drop will make a noticeable difference on the Knight's meter. Obviously it's not being tested at its max rating (no tester does .......
6: Tube DIY Asylum, RE: What kind of multimeter measures 1 ohm? (nt) (0.00)
Posted by Tom Bavis on 2023-10-04, 16:16:48 (98.3.112.80)
It doesn't appear to have "Relative" mode to zero out lead resistance, but you can shot the leads ans and subtract the residual reading. I use a 4-wire Ohmmeter which can resolve .001 Ohm. Good for q .......
7: Tube DIY Asylum, RE: grounding (0.00)
Posted by Tom Bavis on 2023-10-04, 15:58:20 (98.3.112.80)
If you run AC current through the chassis, there will be voltage drop - may be only millivolts, but those millivolts can get amplified as hum... the fix is to make sure no high current loops include t .......
8: Tube DIY Asylum, RE: Internal shield connection (0.00)
Posted by Tom Bavis on 2023-10-01, 15:53:29 (98.3.112.80)
Connect to power supply ground, cathode if more convenient (little signal there). Obviously not the latter if it's a cathode follower. .......
9: Tube DIY Asylum, RE: Parasitic Suppressors (0.00)
Posted by Tom Bavis on 2023-10-01, 15:19:40 (98.3.112.80)
If it uses four 6550s (push-pull parallel), then anode stoppers like those shown above may be necessary. 47 or 51 Ohm carbon, 5 turns or more, in series with all four plate leads. 100 to 220 in series .......
10: Tube DIY Asylum, RE: Help!! Hum on restored vintage tube amp (0.00)
Posted by Tom Bavis on 2023-09-23, 09:57:15 (98.3.112.80)
If touching the chassis has an effect, it's not a ground loop. Reversing the AC wires may help, but it's easier to try grounding the chassis since the ground wire is there. .......
11: Tubes Asylum, RE: EL84 Type Question (0.00)
Posted by Tom Bavis on 2023-08-23, 16:07:04 (98.3.112.80)
Look for an etched code near the bottom - often faint. Some early ones in between the pins. This identifies factory and date (if it's a Philips division). .......
12: Tube DIY Asylum, RE: The sound for this setting, low Ra (0.00)
Posted by Tom Bavis on 2023-07-24, 09:38:04 (98.3.112.80)
Distortion would be low due to the negative feedback. The plate curves become almost straight lines. .......
13: Tube DIY Asylum, RE: If I could fit that thing inside the chassis.... (0.00)
Posted by Tom Bavis on 2023-06-09, 12:07:57 (98.3.112.80)
Also 4.7 @ 1500V and 7.5 @ 1200V in that can size. .......
14: Tube DIY Asylum, RE: If I could fit that thing inside the chassis.... (0.00)
Posted by Tom Bavis on 2023-06-09, 12:04:24 (98.3.112.80)
How about these? https://www.digikey.com/en/products/detail/cornell-dubilier-electronics-cde/UNL10W10K-F/1531169 .......
15: Tubes Asylum, RE: Biasing (0.00)
Posted by Tom Bavis on 2023-06-01, 07:52:35 (98.3.112.80)
Preamp tubes use self-bias - no adjustment needed. They operate at a small fraction of their power rating and signal voltage, so small deviations from optimum are insignificant. Power tubes can use s .......
16: Vintage Asylum, RE: Need pwr Xfmr Id'ed (0.00)
Posted by Tom Bavis on 2023-05-04, 17:31:31 (98.3.112.80)
95-1786 is a Zenith part number. 1960 date code, so it's from a console stereo or TV set. And, lookee what I found (just luck): SFF-2535M, single ended EL84 amp .......
17: Tubes Asylum, RE: Why is there different shunt settings for a rectifier test (0.00)
Posted by Tom Bavis on 2023-04-30, 17:41:47 (98.3.112.80)
Applies to all emission testers - since there's 5V more across one section, it would read higher if settings were the same. Does not apply to indirectly heated rectifiers like 5Z4, 5V4, 5AR4 - those h .......
18: Tube DIY Asylum, RE: Connecting headphones to SET amp (0.00)
Posted by Tom Bavis on 2023-03-25, 09:21:29 (98.3.112.80)
Impedance matching is for maximum power transfer (with headphones: permanent hearing damage). Since headphones are much more sensitive than speakers, hum and noise may be a problem, and the volume con .......
19: Tube DIY Asylum, RE: Build a Power Supply for a McIntosh C8 pre-amp? (0.00)
Posted by Tom Bavis on 2023-02-08, 12:24:26 (216.252.196.34)
Didn't find anything close from Edcor or Hammond. This Antek transformer will give 400V (it's 4 times the current capacity required, only $29). https://www.antekinc.com/as-05t280-50va-280v-transformer .......
20: Tubes Asylum, RE: 7788 brands (0.00)
Posted by Tom Bavis on 2023-01-31, 19:16:03 (216.252.196.62)
First rule: brand on the bottle means little. 7788 was never a high volume tube; probably had few actual makers. Amperex likely imported Philips tubes, maybe from more than one division or factory. RC .......
21: Tubes Asylum, RE: 45 tube substitution (0.00)
Posted by Tom Bavis on 2023-01-12, 12:17:00 (216.252.196.62)
345 would be a Cunningham labeled 45 (Acturus was 145, RCA was 245, etc.). Eventually, the first digit was dropped and everybody made 45s. The 45A was specially made for Silvertone (Sears) - it had a .......
22: Tube DIY Asylum, RE: Magnetic Windings Co. power transformer specs? (0.00)
Posted by Tom Bavis on 2022-10-22, 17:35:31 (98.3.112.80)
Measure winding resistance. I allow 1 watt per heater winding, 2 watts for HV. So a 100 Ohm winding is good for about 140 mA... 100 * (.14)^2 is 1.96 W. Heater windings are tougher, though I have a me .......
23: Tube DIY Asylum, RE: If the wave form was a true square wave... (0.00)
Posted by Tom Bavis on 2022-09-07, 13:19:07 (98.3.112.80)
RMS _is_ equivalent heating. .......
24: Tube DIY Asylum, RE: Measuring Arbitrary Waveforms (0.00)
Posted by Tom Bavis on 2022-09-06, 17:41:30 (98.3.112.80)
The 3400A is specified to 20 MHz - won't be a problem. But most any true RMS meter would do fine - there's very little energy at the highest frequencies. Assuming it's a floating supply, it would be .......
25: Tube DIY Asylum, RE: I tested them before installation (0.00)
Posted by Tom Bavis on 2022-06-28, 07:25:00 (98.3.112.80)
I haven't measured a bad 160P - they're Mylar-paper dielectric. On the other hand, haven't measured a good striped or yellow labeled Black Beauty. .......
26: Tube DIY Asylum, RE: Fast Recovery rectifier- what does it contribute to AUDIO or for tube amp? (0.00)
Posted by Tom Bavis on 2022-06-23, 07:08:46 (98.3.112.80)
A narrow pulse of current flows briefly in the reverse direction in each diode on each AC cycle, so there is a noise source (high order harmonics of 120 Hz). The fast recovery types have a even narrow .......
27: Tube DIY Asylum, RE: interesting read on cap input vs choke input (0.00)
Posted by Tom Bavis on 2022-05-17, 19:15:20 (98.3.112.80)
The writer was considering large transformers - his example was 50 KVA. At this level, three or six phase rectifiers would likely be used. The effect of leakage inductance is not as significant at the .......
28: Vintage Asylum, RE: Electro Voice 12W-1. (0.00)
Posted by Tom Bavis on 2022-05-13, 10:21:28 (98.3.112.80)
You can start by removing the speaker and rotating it 180 degrees, then reinstalling. If the suspension has sagged a little in 60 years, reversing the gravitational pull might realign things. ::: TOPI .......
29: Tubes Asylum, RE: You have a measurement problem (0.00)
Posted by Tom Bavis on 2022-04-28, 06:58:33 (98.3.112.80)
Slow-blow fuses have relatively high resistance - 1/8A Littelfuse is 30 Ohms. Look up the data sheet - it's specified. A few ohms won't make a difference in the bias circuit (or anywhere else a low-va .......
30: Tube DIY Asylum, RE: It is either the cord or the power socket on the amp. (0.00)
Posted by Tom Bavis on 2022-04-24, 10:42:01 (98.3.112.80)
Ye, 1 & 2 were used for the preamp power switch. Jumper them otherwise. .......
31: Tube DIY Asylum, RE: It is either the cord or the power socket on the amp. (0.00)
Posted by Tom Bavis on 2022-04-22, 08:02:19 (98.3.112.80)
The octal power socket has connections for a power switch on the preamp. You'll need to connect pins 1 & 2 for it to turn on. See the AR-425 Sams folder on my web page: http://www.audiophool.com/Made .......
32: Tube DIY Asylum, RE: plate voltage dropping resistrs (0.00)
Posted by Tom Bavis on 2022-03-30, 09:44:41 (98.3.112.80)
Yes, keep the dropping resistor if you need the filtering. Higher plate resistor will give more gain, of course. .......
33: Tube DIY Asylum, RE: plate voltage dropping resistrs (0.00)
Posted by Tom Bavis on 2022-03-30, 07:20:35 (98.3.112.80)
Higher plate load resistor or higher screen voltage will bring plate voltage down. .......
34: Tubes Asylum, RE: Magnavox 197-20 Hum (0.00)
Posted by Tom Bavis on 2022-03-21, 09:12:38 (98.3.112.80)
Hum with inputs shorted? Definitely in the amp. The first cap after the rectifier must be grounded at the same spot as the transformer center-tap - lug on can. The further away it is, the worse the .......
35: Tube DIY Asylum, RE: Can a Voltage Doubler Work Right Off Of Line Voltage? (0.00)
Posted by Tom Bavis on 2022-02-18, 09:17:52 (98.3.112.80)
There are two voltage doubler circuits, commonly called "full wave" and "half-wave" (though both are actually full-wave). With the first, your chassis will be hot with rectified line voltage regardles .......
36: Tubes Asylum, RE: Don't Know But Please Share if You Know How Citation II Prevented (0.00)
Posted by Tom Bavis on 2022-02-11, 13:43:14 (98.3.112.80)
The Citation II has three nested feedback loops, one very short - plate to grid in the driver. Second is from output plates to driver grids, and there's an overall global loop from output transformer .......
37: Tubes Asylum, RE: Advice on power tubes: Two matched pairs but the quad isn't matched (0.00)
Posted by Tom Bavis on 2022-01-22, 08:30:06 (98.3.112.80)
You have two pairs, tested on different testers. But those transconductance numbers may not be directly comparable. Even if they were tested on the same tester, it's still a single point on the tube's .......
38: Tube DIY Asylum, RE: This might be close. (0.00)
Posted by Tom Bavis on 2022-01-16, 11:08:47 (98.3.112.80)
Rather than "regulating" the bias supply, just change a resistor or two to get the voltage into range. Better to have the bias, plate and screen voltages change together with line voltage - if bias vo .......
39: Tube DIY Asylum, RE: Thomas stereo organ amplifier 6973 to 6cz5 conversion (0.00)
Posted by Tom Bavis on 2022-01-15, 14:24:05 (98.3.112.80)
RCA lists the maximum grid resistor as 500K under "Vertical Deflection Amp". Sylvania does the same, but adds "Class A Audio Amp" with a max of 100K (6973 allows 500K). This is the resistor from grid .......
40: Tube DIY Asylum, RE: Current reading different accross choke and resistor??? (0.00)
Posted by Tom Bavis on 2021-12-27, 14:29:46 (98.3.112.80)
The choke resistance will increase when hot - so it will read higher as it warms up. In fact this characteristic is used to measure internal temperature in transformers and choke / motor windings. ::: .......
41: Vintage Asylum, RE: Replacing oddball power transformer - Proton 1100 (0.00)
Posted by Tom Bavis on 2021-12-17, 09:58:16 (98.3.112.80)
What's the screw spacing and height? Main winding would be about 60V CT. .......
42: Tubes Asylum, RE: Tube ID (0.00)
Posted by Tom Bavis on 2021-11-29, 14:01:34 (98.3.112.80)
E-1148 is equivalent to 2C22 and 7193 .......
43: Tube DIY Asylum, RE: Duncan Amps 6L6WGB Data ? (0.00)
Posted by Tom Bavis on 2021-10-28, 19:20:12 (98.3.112.80)
You'll find that operating point on the RCA 6L6GC data sheet. 26 watts at idle. There ARE Philips/Sylvania WGBs with GC plates inside, might be OK with those. And the Russian "5881" coin base are 6L6G .......
44: Tube DIY Asylum, RE: 6b4g filament supply (0.00)
Posted by Tom Bavis on 2021-10-28, 16:16:11 (98.3.112.80)
Yes, you need separate supplies unless you have a separate bias voltage for each. .......
45: Tubes Asylum, RE: What do these numbers mean? (0.00)
Posted by Tom Bavis on 2021-10-22, 08:32:35 (98.3.112.80)
The test data for the TV-7 tester gives instrument settings for a tube and a number which is the minimum meter reading. It's not a percentage or actual transconductance, just a number on the meter. Th .......
46: Tubes Asylum, RE: Boyuurange (0.00)
Posted by Tom Bavis on 2021-10-06, 18:38:41 (98.3.112.80)
If it's part of the IEC connector, there should be a small slot for a screwdriver or knife blade to pry out the fuse holder. Usually the cord must be removed first to allow its removal. .......
47: Tube DIY Asylum, RE: O.T. impedance question. (0.00)
Posted by Tom Bavis on 2021-09-18, 09:02:52 (192.190.167.20)
No, secondary has no effect on idle bias, even primary resistance has almost no effect. If B+ is around 250, 5K primary would be ideal; if 290 or more, 8K would be best. 3.2 Ohms was a common speaker .......
48: Tube DIY Asylum, RE: Losses in Output Transformers (0.00)
Posted by Tom Bavis on 2021-09-17, 10:35:26 (98.3.112.80)
A Dynaco Stereo 770 transformer measured 192 Ohm DCR on the primary; secondary is in proportion, so efficiency is 90%. 300 Ohms with 6.6K will also be around 90%. This is copper loss only; core losses .......
49: Tubes Asylum, RE: THANKS! - RE: Ebay Fake GE 6550A and Brimar 6L6GA (0.00)
Posted by Tom Bavis on 2021-09-15, 11:13:40 (98.3.112.80)
I think they were "faked" by GE and Brimar. Tube orders didn't completely stop even after Western production had... so tubes were found, relabeled, and delivered. And one of the biggest customers, the .......
50: Tube DIY Asylum, RE: dynaclone and triode not offering transformers (0.00)
Posted by Tom Bavis on 2021-09-08, 07:02:43 (98.3.112.80)
I've measured most of the Dynaco transformers with a Wayne-Kerr impedance analyzer- impedance varies with secondary used, I used 8 Ohms. At 1 KHz: A410: 9400 A420: 7200 A430: 4700 A470: 5150 Z565: 830 .......
51: Tubes Asylum, RE: Can a tube cause a physical hum? (0.00)
Posted by Tom Bavis on 2021-09-03, 07:12:14 (98.3.112.80)
I suppose that low emission on one side of a rectifier would result in a net DC flux in the transformer core - which could cause core saturation. But a preamp has such low current that I wouldn't expe .......
52: Tubes Asylum, RE: Question re: replacing 12AX7 with lower gain 5751 (0.00)
Posted by Tom Bavis on 2021-08-24, 12:42:48 (98.3.112.80)
Six 12AX7s in X-100C; different applications in different stages. V1 and V2 are phono preamp, using feedback EQ. Lower gain will result in less accurate equalization at the low end where gain is highe .......
53: Tubes Asylum, RE: Where to find lists of 4v and 5v small signal tubes? (0.00)
Posted by Tom Bavis on 2021-08-24, 12:28:13 (98.3.112.80)
From NJ7P tube database: Triode-pentodes, same basing as 6U8: 4BL8 5EA8 5GH8 5GH8A 5KD8 5MQ8 5U8 Dual triodes, same base as 6DJ8 (5ES8 is variable mu, others may be as well): 4BC8 .......
54: Tube DIY Asylum, RE: I don't think they're the same (0.00)
Posted by Tom Bavis on 2021-07-25, 16:37:12 (98.3.112.80)
Miltary parts are rated at a higher operating temperature, so they have a lower power rating for the same size. The 65 size is rated for 1/2W (mil) or 1 watt (CMF) The 55 size is 1/4W (mil), but 1/2W .......
55: Tube DIY Asylum, RE: Fixed Cathode Bias (0.00)
Posted by Tom Bavis on 2021-07-18, 18:52:09 (98.3.112.80)
As Dave himself pointed out, EFB is unnecessary with a regulated power supply. And regulating screen and bias supplies would have about the same effect, as plate voltage changes have the least effect .......
56: Tubes Asylum, RE: Two-Wire Cord is Extremely Hazardous (0.00)
Posted by Tom Bavis on 2021-07-11, 06:37:44 (98.3.112.80)
Your statement that transformer leakage could kill a person is false - it's minuscule. Yes, you can measure it with a voltmeter - but current is what's dangerous. This sort of design met safety standa .......
57: Tubes Asylum, RE: Two-Wire Cord is Extremely Hazardous (0.00)
Posted by Tom Bavis on 2021-07-10, 17:01:40 (98.3.112.80)
>> "The AC circuit is entirely isolated from the chassis." >> No, it's not. The schematic doesn't show the capacitance to the >> chassis from any of the primary components. Most power transformers t .......
58: Tube DIY Asylum, RE: Unstable SRPP (0.00)
Posted by Tom Bavis on 2021-06-22, 19:06:36 (98.3.112.80)
Power supply time constants may be similar to coupling time constant of C2/R11 - yes, I'd reduce it first, then look at decoupling time constants (more C than just the 2.2 uF, I hope). .......
59: Tube DIY Asylum, RE: 12 volt 6DJ8? (0.00)
Posted by Tom Bavis on 2021-05-29, 14:07:25 (98.3.112.80)
8416 (hard to find, but vacuumtubes.net has 'em) .......
60: Tube DIY Asylum, RE: SE amp with tranny hum, only thru speakers with tube phono preamp (0.00)
Posted by Tom Bavis on 2021-05-20, 18:04:01 (98.3.112.80)
Admiral and Zenith made amps like that, with just output tubes, but could be something in between... transformer numbers could narrow it down. If the tag is from its original cabinet, it's RCA. ::: TO .......
61: Tube DIY Asylum, RE: Amp Identification help needed. (0.00)
Posted by Tom Bavis on 2021-05-20, 18:01:30 (98.3.112.80)
Transformer numbers will include a date code and can confirm that you have the correct service info. No Westinghouse models with that tube lineup on Radiomuseum, but they don't have everything. ::: TO .......
62: Tube DIY Asylum, RE: Photos (0.00)
Posted by Tom Bavis on 2021-04-18, 17:28:19 (216.252.202.59)
I have one of the Greenlee punches with the keyway - I assume it's 1.172" per Amphenol, but can't measure it right now, being 600 miles from my basement... I'll be home next week. .......
63: Tubes Asylum, RE: 6RR8C Tubes (0.00)
Posted by Tom Bavis on 2021-02-14, 14:47:02 (216.252.202.59)
NEC 1966 tube data book, on Frank Philipse's site, shows it as a pentode, equivalent to 404A. Heater on pins 3 & 9. .......
64: Tube DIY Asylum, RE: Tube number origins (0.00)
Posted by Tom Bavis on 2020-12-09, 13:30:42 (98.3.112.80)
The middle letters were assigned more or less in order (rectifiers in reverse, from "Z"), but the single-ended tubes introduced in 1938-41 were an exception. The single letters had mostly run out. Man .......
65: Tube DIY Asylum, RE: Good to know! (0.00)
Posted by Tom Bavis on 2020-11-26, 16:47:59 (98.3.112.80)
The current loop area is what matters. Connecting the laminations together at a single point on each lam will make no difference. Connecting all together at two points, either side of the coil will cr .......
66: Tubes Asylum, RE: What is JEP Amperex? (0.00)
Posted by Tom Bavis on 2020-11-01, 08:26:28 (98.3.112.80)
Just means "JAN by Amperex". You can probably guess what JRC, JTL, JG stood for... others are more obscure. .......
67: Tubes Asylum, RE: Can someone tell me if 7058 tubes will work in my phono stage? (0.00)
Posted by Tom Bavis on 2020-11-01, 08:18:42 (98.3.112.80)
If pin 9 has continuity with pin 4&5, its safe to consider it a 12AX7 equivalent. Both RCA and Sylvania call pin 9: I.C. - "internal connection - do not use" which allows connection to the heater cent .......
68: Tubes Asylum, RE: Help Identifying 12AX7 tubes (0.00)
Posted by Tom Bavis on 2020-09-23, 07:34:46 (98.3.112.80)
I have a Philbrick op-amp with 12AX7 "Computor" tubes with the Tung-Sol code 322. .......
69: Tubes Asylum, RE: Schematic Knight KU-45 Receiver (0.00)
Posted by Tom Bavis on 2020-06-19, 13:04:18 (67.242.174.124)
I volunteer at the Antique Wireless Museum (currently closed but I stop in now and then). I can pick up the KU-45 schematic in the next week or so. email tbavis(at)rochester(dot)rr(dot)com ::: TOPIC:: .......
70: Tubes Asylum, RE: Schematic Knight KU-45 Receiver (0.00)
Posted by Tom Bavis on 2020-06-19, 11:28:00 (67.242.174.124)
Has a "Bogen" look to me - and Bogen DID make some receivers for Allied. If you don't finda anything else, I should have the Sams schematic for Bogen RP-200 (AM/FM simulcast stereo - a year or two bef .......
71: Tube DIY Asylum, RE: Power transformer troubleshooting - would it short out intermittently? (0.00)
Posted by Tom Bavis on 2020-04-30, 17:47:53 (67.242.174.124)
Seems unlikely. I'd swap the rectifer tube. Could short plate-to-plate or plate-to-cathode. Or arc over plate-to cathode, which is more likely if it's gotten weak. .......
72: Tube DIY Asylum, RE: Any 6U10 users or fans out there? (0.00)
Posted by Tom Bavis on 2020-04-19, 19:42:47 (67.242.174.124)
Will have LOTS of gain; you WILL need excellent transformers if feedback takes it down to a reasonable input level. I just built an amp with similar circuit- 26 dB feedback and looks like I need to re .......
73: Tube DIY Asylum, RE: Its rare but yes, that can happen. (0.00)
Posted by Tom Bavis on 2020-03-27, 14:59:56 (67.242.174.124)
3 3/4" is the long dimension; too big. I have a few transformers in the 3" size, but voltage is lower. .......
74: Tube DIY Asylum, RE: Its rare but yes, that can happen. (0.00)
Posted by Tom Bavis on 2020-03-26, 19:33:48 (67.242.174.124)
The power transformer from the HP 200CD audio oscillator has all the same voltages (at a bit higher current) except the bias tap. It's made for vertical mounting but could drop in by swapping end bell .......
75: Vintage Asylum, RE: Any Grundig radio experts here ? Would anyone have a dialcord diagram for a Grundig 102U ? (0.00)
Posted by Tom Bavis on 2020-02-28, 18:02:06 (67.242.174.124)
Both SO105 and 4095 can be found at radiomuseum.org and both have stringing diagrams. Info can now be downloaded by non-members, 3 pages per day. .......
76: Tubes Asylum, RE: rolled off highs (0.00)
Posted by Tom Bavis on 2020-02-02, 14:15:50 (67.242.174.124)
Every transformer maker knew how to make excellent transformers by the early '60s. Fisher output transformers consistently went to 60-70 KHz. Few today match them, not because they can't but because n .......
77: Tube DIY Asylum, RE: Thanks! (0.00)
Posted by Tom Bavis on 2019-08-18, 18:18:48 (67.242.174.124)
Caps with PCBs were usually identified as such (with one of many trade names) - they COST more, and the military and power utilities needed the low-temperature performance that they provided. I doubt .......
78: Vintage Asylum, RE: Anyone have s schematic for a westinghouse hr1053r tube amp? (0.00)
Posted by Tom Bavis on 2019-07-27, 15:45:46 (67.242.174.124)
I find a listing for HF1053, A and B, Sams 527-15 from 1961. Should have it if you need a copy. .......
79: Tube DIY Asylum, RE: what it is??? (0.00)
Posted by Tom Bavis on 2019-06-17, 08:47:38 (67.242.174.124)
Output transformer, probably for for a tape recorder or communications receiver. Three windings, two are marked. Apply 6.3V to the 600 Ohm winding, measure between B+ and Plate terminals, and find the .......
80: Tube DIY Asylum, RE: High Heater Voltage in McIntosh MC30 (0.00)
Posted by Tom Bavis on 2019-01-30, 15:51:08 (72.230.130.107)
I once had to tear down a 10KW transmitter power supply for a screen supply transformer that had two taps brought out to the wrong terminals at the factory. So it's not unheard of. Measure the voltage .......
81: Tube DIY Asylum, RE: Suggestions Please!!!!!!!!!!!!!!!!!!! (0.00)
Posted by Tom Bavis on 2019-01-09, 07:06:24 (72.230.130.107)
Also the "Unlytic" style caps (polypropylene) come in 10 uF, 1000V - they're compact; you could parallel a few. 1 3/8" dia. by about 2" tall. I have some extras. All the filter and decoupling caps wil .......
82: Tubes Asylum, RE: recommended source for Gm values for "new" tubes (0.00)
Posted by Tom Bavis on 2018-12-27, 17:58:20 (72.230.130.107)
If you use a tube tester with filtered adjustable voltages like the Triplett 3444 or an AVO, you can set the operating point and use the gm figure from the tube data sheet. For a Hickock or similar, i .......
83: Tubes Asylum, RE: Which 6CA7 or EL34? (0.00)
Posted by Tom Bavis on 2018-12-03, 17:55:41 (72.230.130.107)
As mentioned, remove R81 (Sams schematic, 1500 Ohms, 5W) to cut 20 mA, that's 5 mA less per tube. If the 12AX7 strings are over 30V, add some resistance in series with each - about 15 Ohms for each vo .......
84: Tube DIY Asylum, RE: Dual primary power trans as isolation transformer (0.00)
Posted by Tom Bavis on 2018-11-26, 07:02:33 (72.230.130.107)
Correct, 1/2 line voltage between wires the full length of the winding. Signal builds many series this way - they had UL but not CSA approval - I doubt they had EU approvals. I found out the hard way .......
85: Vintage Asylum, RE: fisher 680a (0.00)
Posted by Tom Bavis on 2018-11-25, 10:55:39 (72.230.130.107)
Fisher Ambassador V console: http://www.fisherconsoles.com/ambassador%20V.html .......
86: Vintage Asylum, RE: H H Scott 320 Schematic, anyone? (0.00)
Posted by Tom Bavis on 2018-11-25, 10:52:03 (72.230.130.107)
I have a scan of the Sams folder - 10-tubes. tbavis(at)rochester(dot)rr(dot)com .......
87: Tube DIY Asylum, RE: Dual primary power trans as isolation transformer (0.00)
Posted by Tom Bavis on 2018-11-25, 10:40:58 (72.230.130.107)
Not all dual primary transformers have adequate insulation. Some have bifilar primaries, so there are only two thin layers of enamel between you and the power line. Others have the primaries on separa .......
88: Tubes Asylum, RE: OPT imedance numbers (0.00)
Posted by Tom Bavis on 2018-11-15, 19:12:56 (72.230.130.107)
6CZ5 is similar to 6V6. 7-8K for fixed bias, 9-10K for cathode bias, which I assume this is. .......
89: Tube DIY Asylum, RE: It could be a screen grid tap. (0.00)
Posted by Tom Bavis on 2018-10-25, 18:31:21 (67.242.172.34)
It's a hum cancelling tap - commonly used for single-ended outputs. Was cheaper than adding another section of filtering to the power supply. You can use the full winding for about 6K, or leave out th .......
90: Vintage Asylum, RE: What component is this? (0.00)
Posted by Tom Bavis on 2017-12-12, 19:31:24 (67.242.175.122)
Likely an MOV (Metal Oxide Varistor) - an overvoltage protection device. Some years ago I worked at a smallish company and one of my hats was "cal lab". I fixed quite a few Flukes that had been connec .......
91: Tube DIY Asylum, RE: Loktal base rectifier tubes (0.00)
Posted by Tom Bavis on 2017-10-06, 19:26:10 (67.242.175.122)
5AZ4, 125 mA .......
92: Tube DIY Asylum, RE: Couple of PSU questions (0.00)
Posted by Tom Bavis on 2017-09-10, 19:34:14 (67.242.175.122)
I read that as load regulation. Twice the size and weight, twice the voltage drop under load. OK for light loads, using transformers already in hand. .......
93: Tube DIY Asylum, RE: OPT's? (0.00)
Posted by Tom Bavis on 2017-08-14, 17:56:35 (67.242.175.122)
Yes, a "Matrix" amp. A+B from the push-pull transformer, A-B from the smaller SE transformer, and those outputs are added and subtracted to get channel A and B to the speakers. Would work in a small .......
94: Tube DIY Asylum, RE: Free Schematic Drawing Software (0.00)
Posted by Tom Bavis on 2017-06-20, 19:48:04 (68.175.141.137)
Thanks! As I still have an XP machine, I'll have to try it. Later versions of Visio didn't come with electronic symbols - may have been an extra-cost add-on. I created a few schematic symbols, but mos .......
95: Tube DIY Asylum, RE: " Maybe I should be looking for a toroidal transformer" (0.00)
Posted by Tom Bavis on 2017-06-18, 19:31:29 (68.175.141.137)
I have a few of those Hammonds (single primary version) and the secondary has a higher resistance than the primary, about 10%. I would guess that they're designed with about 10% step-up (about 132V un .......
96: Tube DIY Asylum, Re: Disconnecting Relay sound like over-kill (0.00)
Posted by Tom Bavis on 2017-05-03, 07:35:06 (205.167.22.100)
Disconnecting the relay heater after it closes has the additional advantage of resetting the timer. This means that the timing cycle will occur on a brief power interruption as well as cold turn-on. : .......
97: Vintage Asylum, RE: voltage rating for cap in Scott 222D... (0.00)
Posted by Tom Bavis on 2017-03-17, 13:51:40 (205.167.22.100)
Yes, voltage will never be that high here.n A 50V one would do... .......
98: Vintage Asylum, RE: Refubishing old Sherwood S-5000, need schematics (0.00)
Posted by Tom Bavis on 2017-03-03, 10:59:41 (205.167.22.100)
The original S-5000 is in Sams 475-9. You can get a copy from radiomuseum.org - non-members can download 3 pages per day, 10 per month. .......
99: Vintage Asylum, RE: Lafayette LR -1100 receiver stereo indicator lamp (0.00)
Posted by Tom Bavis on 2017-02-28, 12:03:29 (205.167.22.100)
Whoah... we're in squint city! Looks like that transistor is part of IC104. Good luck finding another one of those. .......
100: Vintage Asylum, RE: looking for an SP-10 or SP-20 schematic (0.00)
Posted by Tom Bavis on 2017-02-21, 09:58:09 (205.167.22.100)
They're in Sams, 250 and 253 - I may have one or both - I'll check when I get home. .......
101: Radio Road, RE: Radio Australia Abandoning Shortwave (0.00)
Posted by Tom Bavis on 2017-01-31, 11:27:48 (205.167.22.100)
Well, it WAS eight years ago... it's a HV power supply, 0-500V. I have uploaded a copy to one online test equipment resource, somebody may be looking for it. .......
102: Tube DIY Asylum, RE: PSUD (0.00)
Posted by Tom Bavis on 2017-01-30, 12:58:09 (205.167.22.100)
Likewise, for winding resistance, use half the total (CT to end). .......
103: Radio Road, RE: end of an era (0.00)
Posted by Tom Bavis on 2017-01-30, 11:55:07 (205.167.22.100)
It's not just the power required... transmitters may need replacement parts that haven't been manufactured in years. Somebody I worked with said that it really makes you feel old when you see a buildi .......
104: Radio Road, RE: Radio Australia Abandoning Shortwave (0.00)
Posted by Tom Bavis on 2017-01-30, 11:38:27 (205.167.22.100)
Charles, since this board doesn't do private messages, I just looked for your most recent post. If you're still looking for the Krohn-Hite UHR-225 manual, I just found a copy. Email tbavis(at)rocheste .......
105: Tubes Asylum, RE: 5R4G and 5U4G condenser output value (0.00)
Posted by Tom Bavis on 2017-01-24, 10:13:10 (205.167.22.100)
As other have noted, it's peak repetitive current that's the actual limit. Cathode can only support so much current, and can be damaged it it's exceeded. As with most tube specs, you can usually get a .......
106: Tubes Asylum, RE: This might be a dumb question but that's my specialty (0.00)
Posted by Tom Bavis on 2017-01-20, 08:12:13 (205.167.22.100)
Tube tester readings don't always correlate with amount of usage or remaining life - a tube reading 80% COULD last longer than one reading 100%. And tube testers don't read amplification factor - they .......
107: Tube DIY Asylum, RE: HFAC safety (0.00)
Posted by Tom Bavis on 2017-01-17, 09:08:15 (205.167.22.100)
At frequencies in the megahertz range, the skin effect becomes significant, and current will not go very deep. I have read that if you're in a strong radio frequency field the first thing you'll notic .......
108: Vintage Asylum, RE: Would 7355 OPTs work for PP triode 6AQ5? (0.00)
Posted by Tom Bavis on 2017-01-16, 14:50:50 (205.167.22.100)
I'd expect the 7355 transformers to be about 4K primary. I have a pair of 4K Schumachers that measure fairly good, and have thought about using push-pull parallel 6AQ5s. Four or six per channel? Eithe .......
109: Vintage Asylum, RE: Anyone recognize this transformer? I got a couple from (0.00)
Posted by Tom Bavis on 2017-01-16, 14:44:07 (205.167.22.100)
I think they may be PA amp transformers. Blue and blue/white for plates, red for B+. There could be quite a few secondary taps - 4, 8, 16 and 70V, maybe more. Black, yellow,green, white were common fo .......
110: Vintage Asylum, RE: Dynaco A-25 crossover capacitor (0.00)
Posted by Tom Bavis on 2016-12-08, 08:20:05 (205.167.22.100)
Any film cap is likely to be brighter than the original NP electrolytic, due to lower ESR. So you might be turning the treble control down a notch... but mine were used "up" one step from the beginnin .......
111: Vintage Asylum, RE: low 12AX7 filament voltage in my Fisher X-100-A amp (0.00)
Posted by Tom Bavis on 2016-12-05, 12:37:19 (205.167.22.100)
The lower voltage is by design (though it should be 10-11V DC) - the 12AX7's transconductance will be lower, but noise is reduced too. A matched set of EL84Ms may fix things up with no further action .......
112: Tube DIY Asylum, RE: SE 6CB5 triode : what are the power limits ? (0.00)
Posted by Tom Bavis on 2016-12-02, 11:16:18 (205.167.22.100)
Screen dissipation COULD be a limitation, measure screen current to be sure. A larger resistor connecting screen to plate could help if it's high. .......
113: Tubes Asylum, RE: Question about power transformer specification (0.00)
Posted by Tom Bavis on 2016-12-02, 11:12:46 (205.167.22.100)
Whoaaa... I'm one of those old farts that still read mF as microfarad... .......
114: Tubes Asylum, RE: Question about power transformer specification (0.00)
Posted by Tom Bavis on 2016-11-30, 10:13:22 (205.167.22.100)
Are your planning to LIFT it after you build it? Some serious iron, good for a half an amp, used at 80 mA. Filtering could be better with bigger caps, especially at the output. Which will improve damp .......
115: Tubes Asylum, RE: 150 + 150 secondary?? (0.00)
Posted by Tom Bavis on 2016-11-22, 12:57:51 (205.167.22.100)
Yes. Impedance changes with the square of turns ratio, so twice as many turns gives four time the impedance. .......
116: Tube DIY Asylum, RE: Terry Kath's vintage Knight amp (0.00)
Posted by Tom Bavis on 2016-11-17, 05:57:07 (205.167.22.100)
KN3275B is covered in Sams 964 - I don't have it, but appears to be a schematic only, not a full folder with parts information. It's still in copyright, so you won't find a copy on the web, but you sh .......
117: Tube DIY Asylum, RE: Source for a HP 141a oscilloscope power cord? (0.00)
Posted by Tom Bavis on 2016-11-17, 05:42:21 (205.167.22.100)
I have a few of these, but also have HP instruments that use them. I pick them up whenever I find one at a hamfest - and I find them less and less. .......
118: Tube DIY Asylum, RE: Q: When is Full-Wave not Full-Wave? (0.00)
Posted by Tom Bavis on 2016-10-17, 07:46:50 (205.167.22.100)
You have hit the only real disadvantage of the full-wave doubler vs. the full-wave bridge, as the ESR is higher at 60 Hz than at 120 (not double, though - the few data sheets I can find say 1.2 - 1.7x .......
119: Tube DIY Asylum, RE: Transformer/choke measurement results (0.00)
Posted by Tom Bavis on 2016-10-15, 17:31:43 (67.242.175.122)
Keep in mind that low impedance output impedance is a small-signal value. A cathode follower can deliver the most power into about the same impedance as a plate-loaded stage. Available undistorted out .......
120: Tube DIY Asylum, RE: Capacitance Change with DC Bias (0.00)
Posted by Tom Bavis on 2016-09-08, 12:38:28 (205.167.22.100)
It was Vishay Cera-Mite - this company is a spin-off of Sprague, as they purchased the plants and product lines from them. I grabbed this catalog as I knew they made high-voltage parts. .......
121: Tube DIY Asylum, RE: Capacitance Change with DC Bias (0.00)
Posted by Tom Bavis on 2016-09-07, 11:57:50 (205.167.22.100)
Small SMT packages require very thin dielectric layers, so the field in the dielectric is very high (V/mm in a 10V cap can be much higher than in a 1kV cap!). The first disc ceramic cap (1kV-30kV) cat .......
122: Tubes Asylum, RE: Pentode/Triode Operating Points (6BL8,6U8,6GH8,7199 etc) (0.00)
Posted by Tom Bavis on 2016-08-31, 19:47:47 (67.242.175.122)
My experience (sample of one...) Had a Stromberg ASR120, which uses a gain stage and inverter similar to the Dyna circuit. Rewired the sockets for 6U8, etc., no component value changes. Put in two Amp .......
123: Vintage Asylum, RE: Oh no another speaker wire question (0.00)
Posted by Tom Bavis on 2016-08-29, 14:08:25 (205.167.22.100)
So buy two colors... .......
124: Vintage Asylum, RE: For a mere 7700 dollars you can have some Magnavox amps. (0.00)
Posted by Tom Bavis on 2016-08-17, 05:52:07 (205.167.22.100)
Magnavox used those to prevent VHF parasitic oscillations. Look in any transmitter that uses parallel connected output tubes and you'll see 'em, usually using a large carbon resistor as the winding fo .......
125: Tube DIY Asylum, RE: Grid emission question (0.00)
Posted by Tom Bavis on 2016-08-01, 12:29:08 (205.167.22.100)
Three possibilities, all giving the same symptoms: 1) Gas can result in current flow, upsetting grid bias 2) Conductive deposits inside (on the mica insulators mostly) or outside. 3) Actual grid emiss .......
126: Vintage Asylum, RE: Magnavox 9303 amp question... (0.00)
Posted by Tom Bavis on 2016-07-18, 09:59:35 (205.167.22.100)
I've upgraded a few of these amps. A lighted rocker switch will snap into the opening - you can leave the connector underneath, or cut it off. Two wires from the connector go to the switch, three if i .......
127: Tubes Asylum, RE: Tube ID please... (0.00)
Posted by Tom Bavis on 2016-07-07, 13:03:17 (205.167.22.100)
A tube tester can show the difference between a 12AX7 and 12AU7 - plate structures are the same; the 12AX7 has a closer grid spacing inside. Eye tube is probably EM80 or EM85 - the latter has gotten .......
128: Vintage Asylum, RE: Not correct (0.00)
Posted by Tom Bavis on 2016-07-05, 06:49:18 (205.167.22.100)
My father's '62 Buick Special (and a friend's '61) had the optional lap belts, which stayed under the seats... My mother's '64 Chevy didn't have them - I believe they became standard in '65. Our '69 N .......
129: Tubes Asylum, RE: A lot of the depends on the tester you are using and its operational points (0.00)
Posted by Tom Bavis on 2016-07-01, 18:22:22 (66.67.58.21)
If they used the voltage and current specified on the data sheet, transconductance should match too - so 12AX7 at 250V, 1.2 mA should be 1600, at 100V, 0.5 mA should be 1250. Some tubes will have a gr .......
130: Tube DIY Asylum, RE: Wooo-Hooo...finally scored a Cit.II OPT (0.00)
Posted by Tom Bavis on 2016-06-29, 17:45:29 (66.67.58.21)
A friend has a loose one - I'll get it on the impedance bridge eventually... .......
131: Vintage Asylum, RE: Sherwood S8000 questions (0.00)
Posted by Tom Bavis on 2016-06-10, 11:01:50 (205.167.22.100)
I don't know all the changes between versions, but I do have schematic diagrams for the -II and -IV versions. Both have FM multiplex, if that matters to you - I believe the earliest 8000s are mono. I .......
132: Tube DIY Asylum, RE: Harman Kardon TA5000X output transformers (0.00)
Posted by Tom Bavis on 2016-05-09, 07:05:22 (205.167.22.100)
I measured a pair of these (FT4725698) a while ago - 4120 Ohms loaded with 8 Ohms, a little lower with 4 and 16. They were among the best transformers I've seen - impedance and phase pretty flat to 10 .......
133: Tubes Asylum, RE: another SECO model 7 question... (0.00)
Posted by Tom Bavis on 2016-05-09, 06:48:45 (205.167.22.100)
6BQ7 or 6BK7 as I recall. Eye tube is a shorty 6AF6. .......
134: Tubes Asylum, RE: Tube tester, Seco model 107 (0.00)
Posted by Tom Bavis on 2016-04-20, 17:24:51 (66.67.58.21)
I have the flip chart for tubes that aren't on the panel, but don't think it would be be practical to copy. This tests small-signal tubes for transconductance (assuming they're on the panel) and every .......
135: Tube DIY Asylum, RE: PCB is a byproduct of oil refining, it is dirt cheap! nt (0.00)
Posted by Tom Bavis on 2016-04-15, 14:13:26 (205.167.22.100)
No, PCBs (polychlorinated biphenyls) are not "by-products", they were entirely synthetic - manufactured with a specific process which resulted in several related compounds which were then separated fo .......
136: Tubes Asylum, RE: Help - What do I have? (0.00)
Posted by Tom Bavis on 2016-04-13, 10:34:22 (205.167.22.100)
I would certainly be interested in the amplifier, since I have been collecting Stromberg, and I don't have this model yet. The coils - well, I might use one or two repairing old radios, but most are T .......
137: Tube DIY Asylum, RE: Russian Capacitor containing PCB's (0.00)
Posted by Tom Bavis on 2016-04-13, 10:14:12 (205.167.22.100)
I think it's unlikely that they contain PCBs I've never seen a cap less than 1000V that was marked as containing Pyranol or other PCB trademarkss - and they usually WERE marked, as it cost more, and b .......
138: Tube DIY Asylum, RE: DC Link Capacitors (0.00)
Posted by Tom Bavis on 2016-04-10, 13:40:26 (66.67.58.21)
As you can see from the data sheet, they have a ripple current rating of 5 amps or more. As ripple current will be on the same order as load current for a capacitor input supply, there is certainly pl .......
139: Tubes Asylum, RE: Replacement for screw type speaker terminals? (0.00)
Posted by Tom Bavis on 2016-04-10, 13:29:41 (66.67.58.21)
There are new replacements - but they won't be easy to find. But there may be old stock on Amazon or eBay. Barrier blocks can be used if the screw spacing is the same. Of course you can make your own .......
140: Tubes Asylum, RE: Help - What do I have? (0.00)
Posted by Tom Bavis on 2016-04-10, 13:11:13 (66.67.58.21)
Well, the amp is a Stromberg, so of COURSE I have it. The AR-37 service information can be found on my site: http://www.audiophool.com/MadeInRoch.html The coils and transformers are replacement parts .......
141: Vintage Asylum, RE: Tubes for Bogen RP-230? (0.00)
Posted by Tom Bavis on 2016-03-18, 13:48:25 (65.202.22.70)
Preamp tubes will be 12AX7 or 6EU7, never seen anything else used. Higher value resistors (especially plate resistors, which have high voltage across them) are often off value - I've found them comple .......
142: Tube DIY Asylum, RE: Name This Tube (0.00)
Posted by Tom Bavis on 2016-02-24, 09:20:02 (65.202.22.70)
6111 was a common submini dual triode, medium mu like a 12AU7. 6112 was the high-mu equivalent, more like 12AX7. both were 8-pin, same pinout, I think. There were plenty of others. .......
143: Vintage Asylum, RE: Scott OT rewind (0.00)
Posted by Tom Bavis on 2016-01-06, 13:33:42 (65.202.22.70)
Transcendar has a replacement for the Scott 340A - don't know how close the footprint is, but it's on their web page. If it's too big, their Fisher 400 output might do. If you replace both, you have a .......
144: Vintage Asylum, RE: Which tester to keep ? (0.00)
Posted by Tom Bavis on 2016-01-06, 13:27:35 (65.202.22.70)
Knight will test anything (if it's a 600B or C), though it's "gas" test is of questionable value. Easy enough to test a tube that isn't on the chart if you have a good sample for comparison. But there .......
145: Vintage Asylum, RE: Bogen RR500 Receiver (0.00)
Posted by Tom Bavis on 2015-12-21, 18:52:16 (66.67.58.21)
From the 1954 Radio Shack catalog... .......
146: Tubes Asylum, RE: Why is the 6v6 more useful or used than 6y6 (0.00)
Posted by Tom Bavis on 2015-11-05, 13:47:40 (65.202.22.70)
Efficiency is the main reason 6V6 was used so much - less heater power, less screen current, so it replaced most of the earlier tubes used at the 3-15W output level. It meant that manufacturers could .......
147: Tubes Asylum, RE: 6BQ5 EL84 tube family pinout question (0.00)
Posted by Tom Bavis on 2015-11-02, 08:00:53 (65.202.22.70)
Pin 8 is also shown as I/C on 6BQ5, 7189, 7189A. Russian tubes generally didn't use the (I/C) pins at all - or at least they don't show up as "short" on a tube tester. Others vary by brand and vintage .......
148: Vintage Asylum, RE: tube tester (0.00)
Posted by Tom Bavis on 2015-10-07, 17:06:42 (66.67.58.21)
Good tester using a variant of the Hickock circuit. Easier to use than most, as many tubes have a dedicated socket - set heater voltage, set load, plug in and push the three buttons for shorts, grid l .......
149: Tubes Asylum, RE: What tube subs for a 6BL8 (0.00)
Posted by Tom Bavis on 2015-10-02, 05:05:27 (65.202.22.70)
6LN8 is a near-exact substitute. 6U8 and 6GH8 are usually close enough, and are most common. Plenty of others in the same pinout, 6EA8, 6KD8 and there's a 7199 equivalent: 7687. The direct-coupled cir .......
150: Tube DIY Asylum, RE: Fisher 800C output transformers (0.00)
Posted by Tom Bavis on 2015-09-14, 07:09:47 (65.202.22.70)
I measured 6350 Ohms (1 KHz) on the primary when loaded with 8 Ohms, it'll be higher with 4 or 16 Ohm loads. Impedance is flat: between 6000 and 6500 from 20 Hz to 58 KHz. Phase is +/- 10 degrees from .......
151: Tube DIY Asylum, RE: Help: PS question... 2.5+2.5 in one winding with CTs? (0.00)
Posted by Tom Bavis on 2015-09-10, 18:22:38 (66.67.58.21)
With a single winding, the two cathodes will be tied together, and will have the same bias voltage. OK if they're matched, but you may have hum problems. If he means 2.5-0-2.5V, no that DEFINITELY won .......
152: Tube DIY Asylum, RE: Help: tranny AC voltage to rectifty and get 6.3 volts? (0.00)
Posted by Tom Bavis on 2015-09-09, 08:19:43 (65.202.22.70)
Depends on a lot of things - type of rectifier, size and ESR of capacitor, winding resistance. If it's a little high, you can add a resistor, which can help filtering too. Make it 7V, 2A and you shoul .......
153: Vintage Asylum, RE: I would have to agree (0.00)
Posted by Tom Bavis on 2015-09-09, 08:00:17 (65.202.22.70)
Compare the circuit to the Fisher 50C. .......
154: Tube DIY Asylum, RE: No misunderstanding here. (0.00)
Posted by Tom Bavis on 2015-09-04, 13:42:50 (65.202.22.70)
It can resolve 0.1 mV, but accuracy is not specified below 5% of full range. Seems reasonable to me. If I'm measuring in the mV range, I wouldn't be using a 1V scale - I have an audio voltmeter that g .......
155: Tube DIY Asylum, RE: interesting alternative (0.00)
Posted by Tom Bavis on 2015-08-26, 10:07:34 (65.202.22.70)
Secondary should be rated for voltage to ground and primary to secondary. ONE of these modules would have 1000V to ground, next would have 950V, etc. Safety test for power supplies is typically 1500VA .......
156: Tubes Asylum, RE: 12V6 Pic? (0.00)
Posted by Tom Bavis on 2015-08-21, 06:06:52 (65.202.22.70)
I don't think I've ever seen a metal 12V6 tube, but have plenty of metal 6V6s, 6F6s and 12A6s, all of which would look identical to a metal 12V6, other than the part number label. .......
157: Tube DIY Asylum, RE: Power Transformer Model Inductance (0.00)
Posted by Tom Bavis on 2015-08-12, 08:43:08 (65.202.22.70)
Hum at the speaker is reduced by the ratio of the output transformer - but what's across the primary? Very little with pentode drive, since the high plate resistance of the pentode is in series. For a .......
158: Tube DIY Asylum, RE: How do I determine the fuse current rating for a new amp? (0.00)
Posted by Tom Bavis on 2015-08-05, 06:42:21 (65.202.22.70)
Use alligator clips on the probes. Most meters have a separate input for the highest current range (10A on my Fluke 77). Clip the leads to the power switch terminals and plug it in - switch should be .......
159: Rocky Road, 87 old enough? (0.00)
Posted by Tom Bavis on 2015-07-27, 12:53:40 (65.202.22.70)
Chuck Berry played over 200 monthly shows at the Blueberry Hill in St. Louis - stopped last year, at the age of 87. He was a bit younger when I saw him at the Fillmore East - maybe 1970. .......
160: Tube DIY Asylum, RE: transformer puzzle (0.00)
Posted by Tom Bavis on 2015-07-27, 08:56:43 (65.202.22.70)
Dual primaries for 115/230V were common in military and industrial equipment. But it could be a 400 Hz transformer, or could have some shorted turns. Have had a few like that - local recycler will giv .......
161: Tubes Asylum, RE: Filter caps 5670 pre amp (0.00)
Posted by Tom Bavis on 2015-07-15, 13:57:11 (65.202.22.70)
The negative side of the first 350 uF cap should connect DIRECTLY to the negative side of the recitifer bridge. Keep the ripple current to a loop that does NOT include the chassis. NEVER run any AC cu .......
162: Tubes Asylum, RE: Mounting a resistor on pin 8 of an EL84 (0.00)
Posted by Tom Bavis on 2015-07-15, 13:50:29 (65.202.22.70)
IC - internal connection - could be connected to any element or support inside. EL84s from different makers and vintages vary as to how the IC pins are connected (recent Russian ones don't show any "s .......
163: Tubes Asylum, RE: Thanks! You have any photos of the octals with gold pins? (n/t) (0.00)
Posted by Tom Bavis on 2015-07-08, 08:30:22 (65.202.22.70)
I may have some - remember having a "Lifetime" 6L6GC, among others. .......
164: Tubes Asylum, RE: RCA 417A? (0.00)
Posted by Tom Bavis on 2015-06-27, 17:52:47 (50.134.34.111)
Probably relabeled Raytheon or Amperex. I doubt RCA made this number. .......
165: Vintage Asylum, RE: How to bias this Fisher P/P EL84 amp (0.00)
Posted by Tom Bavis on 2015-06-08, 08:39:13 (65.202.22.70)
In the original console, the (separate) preamp tube heaters were used as the cathode resistor. I assume that there's a large power resistor added for stand-alone use. .......
166: Tube DIY Asylum, RE: potted transformer id help (0.00)
Posted by Tom Bavis on 2015-06-02, 12:31:29 (65.202.22.70)
That's a Fisher part number. About 1958 if their part numbers ran in sequence, which they appear to do. Does not match the Sams parts list for 50A, 80AZ, 100, 125 or 200. But there were various versio .......
167: Tube DIY Asylum, RE: PSUD Playtime (0.00)
Posted by Tom Bavis on 2015-05-27, 07:36:36 (65.202.22.70)
Step response and recovery are most important for amps near class B, where current jumps with drive. A class A amp draws a nearly constant average current, though more output capacitance will help bas .......
168: Vintage Asylum, RE: Jukebox Tube Amp (0.00)
Posted by Tom Bavis on 2015-05-27, 07:21:47 (65.202.22.70)
Some of the Jukebox amps had surprisingly good output transformers. I measured one with OEM P/N 39234-SEI-33061, was made by Stancor (code 138), was flat to about 40 KHz. If that's the one you have le .......
169: Tubes Asylum, RE: How to use dissimilar chokes? (0.00)
Posted by Tom Bavis on 2015-05-15, 12:22:11 (65.202.22.70)
How much current is needed - i.e what's the idle current of the KT90s? As far as order, larger choke followed by smaller cap then smaller choke and larger cap will give a lower circuit "Q", and will h .......
170: Vintage Asylum, RE: Heathkit SA-2 Tube Layout & Knob (0.00)
Posted by Tom Bavis on 2015-05-07, 14:08:13 (65.202.22.70)
Email for the Heath and Sams service data - I have scans of both. I'll see what I have in my knob stash. tbavis(at)rochester(dot)rr(dot)com. .......
171: Tube DIY Asylum, RE: grounding questions.... (0.00)
Posted by Tom Bavis on 2015-04-28, 11:46:07 (65.202.22.70)
Only two ground connections on the power supply - AC cord safety ground and a connection to your signal chassis. Everything else floats - though I'd connect B- to chassis through a 100 Ohm resistor. .......
172: Tube DIY Asylum, RE: loctal pointers? (0.00)
Posted by Tom Bavis on 2015-04-23, 14:17:08 (65.202.22.70)
The nub on the base tells you which direction to pull when you remove one from the socket. .......
173: Vintage Asylum, RE: Analog FM radio may soon go the way of Analog TV (0.00)
Posted by Tom Bavis on 2015-04-21, 13:08:23 (65.202.22.70)
Norway has public broadcasting with five channels of programming and a fair number of listeners using digital radio (DAB) already. Five channels will become 42. Commercial broadcasting in the US is en .......
174: Tubes Asylum, RE: Help with ID (0.00)
Posted by Tom Bavis on 2015-04-06, 12:28:29 (65.202.22.70)
Probably 6SA7, 6SK7, 6SJ7 or 12V 12SA7, 12SK7, all radio tubes introduced in 1938-39. Plug it into a tube tester and test as a 6SA7 or 6SK7 - if it tests dead or very weak, turn up the heater voltage .......
175: Tube DIY Asylum, RE: se 12av5 (0.00)
Posted by Tom Bavis on 2015-04-02, 14:24:56 (65.202.22.70)
A solid-state rectifier with choke input needs a small cap or an MOV to ground after the rectifier for surge suppression. .05uF will do, make it 1000V or more. Shunting the input choke with a lower vo .......
176: Tube DIY Asylum, RE: 6Y6GT/6922 Link to larger schematics and PDF file (0.00)
Posted by Tom Bavis on 2015-03-30, 11:00:33 (65.202.22.70)
My first thought is that you can't get much voltage swing from the split-load inverter - if there's 97 on the gate, about 92 on the source, and the drain resistor will have the same drop, so the drain .......
177: Vintage Asylum, RE: Magnavox EL84 mod suggestions (0.00)
Posted by Tom Bavis on 2015-03-28, 19:32:59 (69.207.169.155)
C6 and C9 are for bass boost, probably unwanted if the amp is used stand-alone. The gain EQ was to compensate for cartridge, speaker, passive tone controls. The bass control does nothing unless it fol .......
178: Tubes Asylum, RE: open pinouts on 6BQ5/EL84/7189... (0.00)
Posted by Tom Bavis on 2015-03-09, 06:39:06 (65.202.22.70)
They vary by brand and vintage. Recent Russian EL84s seem to have no connections, earlier US and European ones may or may not - so the pins may show "short" on a tester or not. The 7189A does use the .......
179: Tubes Asylum, RE: Dynaco ST70 OPT failed secondary? (0.00)
Posted by Tom Bavis on 2015-03-09, 06:34:39 (65.202.22.70)
Would seem impossible since it's heavy gauge wire - the solder joints may be a weak link, though. If so, the other taps may be OK. I HAVE heard of primary failures - with a section having high resista .......
180: Vintage Asylum, RE: Oscilloscope For Tube Radio Repair & Alignment (0.00)
Posted by Tom Bavis on 2015-03-05, 18:31:21 (69.207.185.84)
As usual, the Sencore probes are missing, so you can't use the voltmeter with the same probe... You could use a separate probe, no better than using a separate DVM. A good set of Sencore probes will b .......
181: Tubes Asylum, RE: 6G5 & 6E5 (0.00)
Posted by Tom Bavis on 2015-03-03, 08:12:46 (65.202.22.70)
Bright area may overlap on a strong station. But it is the same except for sensitivity. It MAY be possible to add a resistor divider to lower input level, using resistors in the megohm range. ::: TOPI .......
182: Vintage Asylum, RE: Should I buy this (0.00)
Posted by Tom Bavis on 2015-03-03, 07:57:42 (65.202.22.70)
Service manual is online at Fisherconsoles.com, but you might have to look for another model with the same chassis. .......
183: Tube DIY Asylum, RE: Bridge vs. Voltage Doubler for 4W SET (0.00)
Posted by Tom Bavis on 2015-02-24, 05:37:57 (65.202.22.70)
The transformer will draw magnetizing current when unloaded, which could be as much as a few hundred mA if it's rated for 60 Hz only. A 50/60 Hz design will have more headroom, and will draw less. A c .......
184: Vintage Asylum, RE: help with Fisher KX-200 (0.00)
Posted by Tom Bavis on 2015-02-16, 11:13:25 (69.207.185.84)
As Jim said, ignore the grid voltage - it's idle current you need to set. If you're using a low-cost DVM, it may read low with the 270K grid resistor in series - but should measure the voltage at the .......
185: Tube DIY Asylum, RE: paper in oil caps with grounded case (0.00)
Posted by Tom Bavis on 2015-02-09, 08:01:07 (65.202.22.70)
Make sure they're not "feedthrough" caps (continuity from terminal to terminal, cap to ground). I have some like that as well as conventional caps with grounded case. .......
186: Tube DIY Asylum, RE: Interesting setup (0.00)
Posted by Tom Bavis on 2015-02-07, 11:47:06 (69.207.185.84)
For those that haven't seen this phase inverter before, it's the "floating paraphase" or "self-balancing paraphase". The CRCR forms a high-pass filter, rolling off at a few Hz. Probably needed for sub .......
187: Tube DIY Asylum, RE: Flywheel redux (0.00)
Posted by Tom Bavis on 2015-02-02, 08:06:32 (65.202.22.70)
Completely different... the choke input puts out much lower voltage, needs a higher transformer voltage for equivalent output. The added small choke and capacitor doesn't add much filtering, but impro .......
188: Tube DIY Asylum, RE: Flywheel redux (0.00)
Posted by Tom Bavis on 2015-02-01, 19:10:17 (69.207.185.84)
Compared to capacitor input, the conduction angle is greater, the peak current is less, the RMS current in the transformer is less, and the output voltage is greater. The effect is not large, but easi .......
189: Tubes Asylum, RE: As power tubes age ... (0.00)
Posted by Tom Bavis on 2015-01-22, 08:05:08 (65.202.22.70)
Transconductance drops with age, and that affects the operating point, so bias adjustment is required. Pairs may not age equally, so AC balance may not be ideal even if you can bias both tubes separat .......
190: Tube DIY Asylum, RE: Damper diodes (0.00)
Posted by Tom Bavis on 2015-01-15, 07:27:23 (65.202.22.70)
Transformer inrush can be significant with no load - it can be higher than charging inrush in a power supply. However, its occurrence and magnitude is random - it depends on the phase of the AC at tur .......
191: Tube DIY Asylum, RE: Damper diodes (0.00)
Posted by Tom Bavis on 2015-01-14, 12:04:39 (65.202.22.70)
An NTC inrush limiter will help with transformer inrush. A transformer may saturate on the first half-cycle of AC if any remaining magnetism in the core is in the same direction as that from the appli .......
192: Vintage Asylum, RE: Laments - January 1979 Audio Magazine (0.00)
Posted by Tom Bavis on 2015-01-08, 06:05:49 (65.202.22.70)
Bureau of Labor Statistics says that $12,000 in 1979 is equivalent to $39,000 today. So you gets a Miata and some change... .......
193: Tube DIY Asylum, RE: pri. 110V power transformer (0.00)
Posted by Tom Bavis on 2015-01-06, 06:51:48 (65.202.22.70)
They could use the same core. For 220V, the primary would need twice as many turns to have the same magnetic flux in the core. But it could be made with smaller wire, since full load current will be h .......
194: Tube DIY Asylum, RE: pri. 110V power transformer (0.00)
Posted by Tom Bavis on 2015-01-05, 09:56:15 (65.202.22.70)
While it might seem that you could use a 120V : 6V transformer as 240 : 12V, it's not possible in practice. Doubling the voltage will double the magnetic flux in the core, probably exceeding the level .......
195: Vintage Asylum, RE: Weird Vintage Piece of the Day (0.00)
Posted by Tom Bavis on 2014-12-29, 08:56:48 (50.134.34.111)
This may be a three channel amp - P-P for bass center channel, SE for R/L treble. .......
196: Tubes Asylum, RE: Eico 667 Compactron setting (0.00)
Posted by Tom Bavis on 2014-12-23, 14:23:31 (50.134.34.111)
Use 6LF6 settings but set heater to 12.6V. .......
197: Vintage Asylum, RE: Really would like to find a couple more Thordarson catalogs and manuals (0.00)
Posted by Tom Bavis on 2014-12-18, 17:51:56 (50.134.34.111)
... And of course bunkerofdoom.com and my site audiophool.com? .......
198: Tube DIY Asylum, RE: Magnavox 9302-00 Schematic (0.00)
Posted by Tom Bavis on 2014-12-12, 08:45:10 (65.202.22.70)
Yes, dual log-taper pot will be needed - 500K is probably best, as the phono stage has a high output impedance. If the 750 Ohm balance control R117 is installed, leave it as-is - if not, you need to a .......
199: Tube DIY Asylum, RE: "self resonant frequency" of an inductor (0.00)
Posted by Tom Bavis on 2014-11-25, 12:45:44 (65.202.22.70)
1 KHz doesn't sound physically possible - to resonate 100 mH at 1 KHz would require a winding capacitance of .25 uF. 100 pF might be possible, depending on size, and would resonate it at 50 KHz. ::: T .......
200: Tubes Asylum, RE: 6GT5 conversion (0.00)
Posted by Tom Bavis on 2014-11-21, 18:07:07 (69.207.176.88)
$15 is expensive? ESRC price. Of course you'll need new sockets... might be less work to add a 12VCT transformer in series with the heater to the sockets and then 12GT5 ($3) and 17GT5 ($5) would be op .......
201: Tube DIY Asylum, RE: FREE for pickup - RCA tuner and stereo SE 6v6 amp (0.00)
Posted by Tom Bavis on 2014-11-16, 14:29:26 (69.207.176.88)
I'd certainly be interested for the cost of shipping - I can give you a FedEx account number so that you can just drop it off. I'll be headed to SW Virginia in a few weeks, but won't get near DC. tbav .......
202: Tube DIY Asylum, RE: Scott LC21 Volume Control gain problem (0.00)
Posted by Tom Bavis on 2014-11-12, 14:14:32 (65.202.22.70)
100K will give a 17% gain reduction, 1.5 dB. 470K will give a 6 dB reduction, 1 meg about 10 dB. .......
203: Tubes Asylum, RE: Look towards the bottom of the glass (on the side) (0.00)
Posted by Tom Bavis on 2014-11-12, 14:03:35 (65.202.22.70)
Asterisk (*) indicates that they came from Long island. Second character in second row is 1 digit year (2 : 1962, possibly '72) .......
204: Tube DIY Asylum, RE: Eimac fans: free book of tech notes (0.00)
Posted by Tom Bavis on 2014-11-10, 08:27:09 (65.202.22.70)
Frank Philipse may be interested if it's not on his site already. .......
205: Vintage Asylum, RE: Anyone know the numbering system for Freed chokes? (0.00)
Posted by Tom Bavis on 2014-11-10, 08:19:24 (65.202.22.70)
Freed's catalog parts were 2-3 letters and a number - not just a number. Those may be RCA numbers or Freed's OEM numbering, each new design assigned the next number on the list. .......
206: Vintage Asylum, RE: Refinishing a table radio questions (0.00)
Posted by Tom Bavis on 2014-11-04, 07:53:32 (65.202.22.70)
Looks like clear lacquer on the front (wood has darkened considerably) and brown toned lacquer on the rest. I'd say it needs stripping (with lacquer thinner). For electrical restoration, I have the Ph .......
207: Vintage Asylum, RE: Will UTC S-15 work for pp 1626? (0.00)
Posted by Tom Bavis on 2014-10-30, 05:25:42 (65.202.22.70)
Catalog says primary is 4K, 5K or 10K. It'll be hard to find anything higher than 10K, probably the best impedance for P-P 1626. .......
208: Tube DIY Asylum, RE: Anyone knows a good place to buy film capacitor assortments? (0.00)
Posted by Tom Bavis on 2014-10-24, 10:21:55 (65.202.22.70)
Justradios.com or radioantiques.com (Bob may have only polyester...) .......
209: Tubes Asylum, RE: Genalex 300b (0.00)
Posted by Tom Bavis on 2014-10-24, 10:17:52 (65.202.22.70)
Genelex 300Bs, Tung-Sol KT66s - what's next? Telefunken 2A3s? .......
210: Tubes Asylum, RE: Any ideas what tubes these are? (0.00)
Posted by Tom Bavis on 2014-10-24, 10:14:21 (65.202.22.70)
First could be one of about 30 numbers... 6AU6 or 12BA6 most likely. Metal one doesn't have a lot of pins - 6J5 maybe? Third looks like a GE 6V6. Next could be a 6V6G, 6Y6G, 6F6G... Next maybe a 26 - .......
211: Vintage Asylum, RE: Dad Blame it! (0.00)
Posted by Tom Bavis on 2014-10-24, 10:09:07 (65.202.22.70)
Sams folder 802-5 (1966) covers the Admiral - too late to be in my files. This one might be close: http://techpreservation.com/schematics/67/67_Admiral_6M4A_6.djvu .......
212: Tube DIY Asylum, RE: Pilot Radio Schematic (0.00)
Posted by Tom Bavis on 2014-10-15, 16:38:56 (69.207.176.88)
email tbavis(at)rochester(dot)rr(dot)com. I believe this is the amp from model 4500. .......
213: Vintage Asylum, RE: Schematic for an Olson AM-240-A amp? Huge OT iron! (0.00)
Posted by Tom Bavis on 2014-10-14, 11:46:42 (65.202.22.70)
Sams folder 565-7 covers the Calrad SA-30. Has potted transformers, tube rectifier, 6BM8s. Does look similar from the front though... .......
214: Vintage Asylum, RE: Pilot 602 (0.00)
Posted by Tom Bavis on 2014-10-01, 13:46:46 (65.202.22.70)
There was a model 602, covered in the 1961 Sams folder 525-11, and a 602M, covered in 1963 folder 625-12. Haven't heard either one. Output transformers in the 602 were on the small side, wouldn't expe .......
215: Vintage Asylum, RE: flea mkt 6L6gc army amplifier find (0.00)
Posted by Tom Bavis on 2014-10-01, 08:53:59 (65.202.22.70)
May sound like a tank as well... .......
216: Tube DIY Asylum, RE: Vintage SE OPT hook up confusion (0.00)
Posted by Tom Bavis on 2014-09-23, 06:33:22 (65.202.22.70)
63 Ohms seems awfully low for a primary resistance - are they treble transformers for bi-amp? Moto made quite a few three channel amps. And 48 ohms seems awfully high for a secondary. But likely was u .......
217: Vintage Asylum, RE: Source For Vintage Marantz Schematics? (0.00)
Posted by Tom Bavis on 2014-09-13, 17:18:56 (67.253.240.216)
Sams covered the later solid-state models very well in the MHF (Modular Hi Fi) books, but only two tube-era models were covered. The 8B schematic (only) is in the #915 Servicer, and the Consolette ("M .......
218: Tubes Asylum, RE: Power Tubes For A Fisher 500 Mono Receiver (0.00)
Posted by Tom Bavis on 2014-09-09, 19:43:20 (67.253.240.216)
Later 500s used 5881s from the factory - a friend has one, and 5881 is screened next to the sockets. If I recall correctly, the 5881s will be red-plating if replacing the EL37s directly, and there was .......
219: Vintage Asylum, RE: Need schematic for Bell 3030 6V6 tube integrated amplifier... (0.00)
Posted by Tom Bavis on 2014-09-09, 19:36:10 (67.253.240.216)
email - tbavis(at)rochester(dot)rr(dot)com .......
220: Tube DIY Asylum, RE: TO-220 tab leaking to heatsink? (0.00)
Posted by Tom Bavis on 2014-09-06, 19:08:43 (67.253.240.216)
PC CPUs usually use a silver-filled compund which is conductive, both thermally and electrically. Any residue of that may make the silicone compound resistive. We test TO-220 devices at work for brea .......
221: Tubes Asylum, RE: Did I miss any of the 12AX7 replacements? (0.00)
Posted by Tom Bavis on 2014-09-02, 12:14:56 (65.202.22.70)
12BZ7 doesn't have higher gain - it has higher transconductance but gain (mu or amplification factor) is 100, same as 12AX7. They are reputed to be quite microphonic, watch out for that. Heater curren .......
222: Tube DIY Asylum, RE: Are my ITs ok for this schematic? (0.00)
Posted by Tom Bavis on 2014-08-22, 09:16:02 (65.202.22.70)
The Lundahls are specified for 25 Hz to 40 KHz if gapped for 10 mA and driven by a 14K impedance. Since two sections of 6SL7 in parallel will be 22K, the low end (and likely high end) will be reduced. .......
223: Tube DIY Asylum, RE: How do I double the voltage on diodes? Parallel or series? (0.00)
Posted by Tom Bavis on 2014-08-21, 07:38:34 (65.202.22.70)
You need 1200V bare minimum - 1600V would be better... why not use 1000V diodes in series? I wouldn't trust 600V parts in series to take 1200V peak. And why an 8A rectifier? A 1A or 4A part will be ea .......
224: Vintage Asylum, RE: Unknown speaker EIA manufacturer number (0.00)
Posted by Tom Bavis on 2014-08-19, 09:05:56 (65.202.22.70)
256 is not listed on the 1953 , 1957, 1962 EIA code lists I have. On the 1946 list it's Panelyte division, St. Regis Paper corporation. Perhaps it's a 6- digit part number, not a code? .......
225: Tubes Asylum, RE: ECF80/6BL8= which separate pentode +triode (0.00)
Posted by Tom Bavis on 2014-08-05, 06:12:46 (65.202.22.70)
6AU6 has a bit less transconductance than the pentode in the 6BL8, 6BC5 is about the same, 6AH6 bit more. All share the same pinout. The triode has twice the transconductance of a 12AU7, same mu, so p .......
226: Tube DIY Asylum, RE: Looking at PP amp designs (0.00)
Posted by Tom Bavis on 2014-08-04, 06:35:39 (65.202.22.70)
Cathode bias requires constant cathode current: class A. Peak current in either tube is twice the idle current - as one approaches peak, the other approaches cutoff. Fixed bias allows biasing the tub .......
227: Tubes Asylum, RE: tube compatibility (0.00)
Posted by Tom Bavis on 2014-07-30, 06:54:35 (65.202.22.70)
6C6 is close except for heater voltage - 6C6 is 6.3V, 310 is 10V. Will need a dropping resistor or other adjustment. .......
228: Tubes Asylum, RE: Voltage Doublers (0.00)
Posted by Tom Bavis on 2014-07-23, 11:46:09 (65.202.22.70)
Yes, there's no way to implement choke input with the voltage doubler (there is a "current doubler" configuration with two chokes that cuts voltage in half though - not likely to be useful for high vo .......
229: Tubes Asylum, RE: Voltage Doublers (0.00)
Posted by Tom Bavis on 2014-07-23, 05:57:04 (65.202.22.70)
Assuming proper transformers of the same VA rating, a voltage doubler and full-wave bridge will perform exactly alike: same output current, same supply impedance, same regulation, ripple voltage, etc. .......
230: Tube DIY Asylum, RE: What is the best way to hook up 2 rectifiers? (0.00)
Posted by Tom Bavis on 2014-07-12, 16:50:47 (50.134.34.111)
Preferred connection is to parallel the two plates inside each tube. Sections more likely to be matched, and currents will stay matched reasonably well if one is replaced. And there won't be 640VAC ac .......
231: Tube DIY Asylum, RE: Can I use these "Output Autoformers" Triad S-46A (0.00)
Posted by Tom Bavis on 2014-06-27, 13:07:03 (65.202.22.70)
Yes, SE parafeed is about the only choice .......
232: Tubes Asylum, RE: Tube Advice Requested (0.00)
Posted by Tom Bavis on 2014-06-19, 10:56:35 (65.202.22.70)
Was a common TV tube, but of course hasn't been made in many years. The supply will dry up eventually, but they're cheap for now. 6MF8 and 6MY8 are very similar, but are much less common. It's essenti .......
233: Tube DIY Asylum, RE: New production Sprague Vitamin Q Type 196P (0.00)
Posted by Tom Bavis on 2014-06-18, 08:30:20 (65.202.22.70)
False. PCBs were less common than people seem to think. PCBs were only used in large high voltage capacitors, 1000V and up. And they were generally labeled with a trade name like "Dykenol", etc. ::: T .......
234: Tubes Asylum, RE: Can I use a 5R4GY in an amp made for 5U4G/5U4GB/U52 ? (0.00)
Posted by Tom Bavis on 2014-06-15, 10:53:11 (67.253.240.216)
5R4 MAY be OK, depending on circuit values. Peak current limit is lower for 5R4. Peak current depends on (1)transformer voltage (2) transformer winding resistance plus any other limiting resistance (3 .......
235: Tubes Asylum, RE: Harmon Kardon Tube Receiver HK223 (0.00)
Posted by Tom Bavis on 2014-06-09, 10:26:16 (65.202.22.70)
Looks like it says "Stereo Recital" on the panel, which was the TA-224. Sams index has it in 1961, though it could have been a little earlier. Push-pull 6V6 for about 12 watts per channel. Those litt .......
236: Tubes Asylum, RE: Harmon Kardon Tube Receiver HK223 (0.00)
Posted by Tom Bavis on 2014-06-09, 09:07:37 (65.202.22.70)
Never heard of a HK223... there were the lower powered TA224 and TA230, the TA260 using 7355 output tubes. I don't think there ever was a stereo receiver that used 6L6s - by the time of stereo, smalle .......
237: Vintage Asylum, RE: I got a D in dial string 101 (0.00)
Posted by Tom Bavis on 2014-05-28, 11:58:54 (65.202.22.70)
Got a chassis number? Should be in the Sams folder... .......
238: Vintage Asylum, RE: Altec 340a and 440b - Found (0.00)
Posted by Tom Bavis on 2014-05-08, 05:37:54 (65.202.22.70)
I have schematics for both if you need them - tbavis(at)rochester(dot)rr(dot)com .......
239: Tube DIY Asylum, RE: feedback/balance control on a Magnavox pp el84 (0.00)
Posted by Tom Bavis on 2014-05-07, 13:34:41 (65.202.22.70)
Replace the (750 Ohm) pot with two 390 Ohm resistors to ground - this will give the proper amount of feedback. Low frequency oscillation (motorboating) is a result of low-frequency phase shift and too .......
240: Tube DIY Asylum, RE: thanks! (0.00)
Posted by Tom Bavis on 2014-04-24, 13:23:34 (65.202.22.70)
Assuming you have enough heater power, there are higher rated damper diodes that will plug in and work - same pinout as 6AX4. 6AU4, 6DE4, 6CQ4, etc. But sounds like 6AX4s will be fine. .......
241: Tubes Asylum, RE: 6CG7 sub for 6N1P sub for 6922? (0.00)
Posted by Tom Bavis on 2014-04-24, 13:17:05 (65.202.22.70)
I don't think there's any risk of damage to the equipment unless you plug in a tube of different pin connections. Certain swaps might be hard on the tubes, though it's likely in those cases that it wo .......
242: Tubes Asylum, RE: 6CG7 sub for 6N1P sub for 6922? (0.00)
Posted by Tom Bavis on 2014-04-24, 06:05:36 (65.202.22.70)
Three very different tubes, all with the same pin connections. The 6CG7 and 6P1 are closer than the 6922/6GDJ8, but still quite different. If a circuit is optimized for any one of these, a different o .......
243: Tube DIY Asylum, RE: Power switch wiring (0.00)
Posted by Tom Bavis on 2014-04-16, 05:41:46 (65.202.22.70)
Current safety standards call for live wire to connect to back terminal of fuse holder (to avoid exposing a "hot" terminal if fuse is removed), then side terminal to power switch, then to load. A seco .......
244: Vintage Asylum, RE: Stromberg AR411 question (0.00)
Posted by Tom Bavis on 2014-04-12, 18:47:22 (67.253.240.216)
I've had a few transformers and chokes that WORKED (sort-of) in circuit but were open. I imagine that there was an arc-over at the break which carbonized the paper insulation and conducted... they did .......
245: Vintage Asylum, RE: Sherwood S-8000 receiver III vs IV (0.00)
Posted by Tom Bavis on 2014-04-12, 16:53:05 (67.253.240.216)
They changed from 12AX7s to 6EU7s in the -IV - equivalent with a different pin-out. Email for a schematic: tbavis(at)rochester(dot)rr(dot)com .......
246: Tubes Asylum, RE: Hey Mikey - S-1000 (0.00)
Posted by Tom Bavis on 2014-04-09, 18:08:34 (67.253.240.216)
The S-1060 was the one I was thinking of with SIX EL84s. S-4000 was a single pair in P-P. Looks like the original S-1000 was 1957, at least that's when Sams covered it in 345-1. 12AX7s, 12AU7 driver, .......
247: Tubes Asylum, RE: Tube Power Amps ... power supply capacitance. (0.00)
Posted by Tom Bavis on 2014-04-09, 17:50:40 (67.253.240.216)
Since stored energy is 1/2 C * V^2, the difference may not be as big as it appears. 100 uF at 400V holds the same energy as 10,000 uF at 40V. As mentioned, tube rectifiers have peak current limitation .......
248: Tubes Asylum, RE: 6AQ5 PP amps (0.00)
Posted by Tom Bavis on 2014-04-09, 05:55:46 (65.202.22.70)
Use up your 7-pin sockets! 6J6 as long-tail pair phase inverter. 6C4 or triode wired 6AU6 for a bit more gain. Direct coupled as per Mullard/EICO circuit. If you'd rather use 9-pin, 12AV7 is equivalen .......
249: Vintage Asylum, RE: Oh check out this Sherwood inegrated amp that very few have ever seen. (0.00)
Posted by Tom Bavis on 2014-04-08, 13:23:28 (65.202.22.70)
Model S-1060 - around 1960 vintage. Covered in Sams 469-11. .......
250: Tubes Asylum, RE: Hey Mikey - S-1000 (0.00)
Posted by Tom Bavis on 2014-04-08, 06:10:49 (65.202.22.70)
I'll see if Sams covers that one - Sherwood schematic is on my page. S-4000 is a unique one with 6 x EL84, but S-4400 is the really strange one - stereo preamp and single PPP EL84 power amp. S-360 was .......
251: Tubes Asylum, Hey Mikey - S-1000 (0.00)
Posted by Tom Bavis on 2014-04-07, 13:21:16 (65.202.22.70)
Saw your request for a schematic on Radiomuseum.org If you're looking for the original 6L6 version, I should have the Sams (and the other two Sams folders for that matter... I assume they're the quad .......
252: Tube DIY Asylum, RE: 7199 vs. EF86 and 12AU7 (0.00)
Posted by Tom Bavis on 2014-03-15, 20:35:29 (67.253.240.216)
Ned started tubezone.net - now selling tubes in England? .......
253: Tube DIY Asylum, RE: Probably a ????? that was asked a million times (0.00)
Posted by Tom Bavis on 2014-03-14, 17:22:33 (67.253.240.216)
Yes, it's called a regulated power supply. Seldom used in power amps due to the cost and extra power required. What's happening is that you change the current in one power tube, and the unregulated po .......
254: Tube DIY Asylum, RE: No negative bias voltage problem (0.00)
Posted by Tom Bavis on 2014-03-05, 18:50:56 (67.253.240.216)
The circuit you have won't work with a full-wave bridge. Either change the dropping resistor to a cap, or you can try the reversed transformer - it will draw very little current, especially if you run .......
255: Tube DIY Asylum, RE: No negative bias voltage problem (0.00)
Posted by Tom Bavis on 2014-03-05, 12:42:52 (65.202.22.70)
The circuit you're using won't work with a full-wave bridge (though it should work with a full-wave center-tap circuit). The voltage at the transformer (AC terminal of bridge) goes from -0.7V (when th .......
256: Tube DIY Asylum, RE: tweaking cheaper output trans fixings for greater magnetic freedom (0.00)
Posted by Tom Bavis on 2014-03-01, 18:17:56 (67.253.240.216)
I doubt that there will be a measurable or audible difference - the bolts aren't really in the magnetic circuit, being at right-angles to the major flux path. If you do replace them, be sure to insula .......
257: Vintage Asylum, RE: THose will not work for your application (0.00)
Posted by Tom Bavis on 2014-03-01, 18:03:24 (67.253.240.216)
CL-80 is the one I used in the Fisher - CL-90 is rated 2.0 amps maximum, and the CL-80 is 3 or 4A - I forget. And the fuse can be reduced to a 2.5A slow-blow. .......
258: Tube DIY Asylum, RE: Tube sockets (0.00)
Posted by Tom Bavis on 2014-02-27, 05:36:24 (65.202.22.70)
Yes, I have some mounting rings like that, but have only found them in military equipment. "C" shaped with 4-40 tapped holes. One other possible fix - use hex standoffs as mounting nuts - hold it in a .......
259: Tube DIY Asylum, RE: Material/product for mounting coupling and bypass caps (0.00)
Posted by Tom Bavis on 2014-02-21, 05:33:50 (65.202.22.70)
Double-sided foam tape works well for "box" type caps. The silicone is called RTV (short for Room Temperature Vulcanizing). One version is sold as aquarium caulk, another contains a fungicide and is s .......
260: Tubes Asylum, RE: bogen with phono (0.00)
Posted by Tom Bavis on 2014-02-12, 17:44:07 (67.253.240.216)
If you restore it with proper components you'll have the basis for a good guitar amp. The "Challenger" series did not have the quality transformers that many of the Bogen amps did have. They were desi .......
261: Vintage Asylum, RE: In Search of Fisher 50 PR-C Schematic/Owners Manual-not 50-PR... (0.00)
Posted by Tom Bavis on 2014-02-09, 09:28:56 (67.253.240.216)
50PR is listed in the Sams index, folder 262-8, no mention of PR-C. Don't have that one myself... .......
262: Tube DIY Asylum, RE: I always wonder if ... (0.00)
Posted by Tom Bavis on 2014-02-06, 13:31:54 (65.202.22.70)
This should be fine for the MO-30, as I wold expect to draw less than 1A (CL-90 is rated 2A max). I often can use a smaller fuse after installing an inrush limiter, as original was oversize to handle .......
263: Vintage Asylum, RE: How much is a done-up one worth $US and do they support 240/50hz? (0.00)
Posted by Tom Bavis on 2014-01-28, 06:13:55 (65.202.22.70)
Yes for phase reverse switch, 240V transformer is not standard for MX-110 - don't know about Z model, but I'm sure it was available at least as an option. The transformers have become quite rare it se .......
264: Tubes Asylum, RE: Are these Bugle Boys real? (0.00)
Posted by Tom Bavis on 2014-01-21, 06:01:40 (65.202.22.70)
Richardson now owns the Bugle Boy and Amperex trademarks, so they can put them on anything they choose. So they are GENUINE but not VINTAGE. The date of 6/20/01 tells me that these are recent producti .......
265: Tubes Asylum, RE: Halo's and getters (0.00)
Posted by Tom Bavis on 2014-01-20, 13:49:42 (65.202.22.70)
To avoid confusion Call the internal structure in the tube the "getter ring" And call the flash on the glass the "gettering" .......
266: Vintage Asylum, RE: Sherwood S-5500 schematic? (0.00)
Posted by Tom Bavis on 2014-01-17, 06:29:01 (65.202.22.70)
Original 5500? I have the Sams, but will have to scan it. Email tbavis(at)rochester(dot)rr(dot)com .......
267: Tube DIY Asylum, RE: Look how nice Pete Millets new boards fit on the MK3s (0.00)
Posted by Tom Bavis on 2014-01-15, 05:46:04 (65.202.22.70)
Mike, as George (Tubelab) noted, it goes the other way up. Compactron socket goes on opposite side from silkscreen. Other components can go on either side. I THINK the 6U10 will work in this as well.. .......
268: Vintage Asylum, RE: Just found in my Christmas cleaning (0.00)
Posted by Tom Bavis on 2013-12-28, 20:15:48 (67.253.240.216)
4000-R is the tuner from the President console, top of Fisher's console line in 1961. It may be equivalent to one of the component tuners - I'm not sure which. The President console was $2600 in 1961 .......
269: Vintage Asylum, RE: Got the 58 dollar tube receiver today. (0.00)
Posted by Tom Bavis on 2013-12-21, 09:52:17 (67.253.240.216)
If you're not in too much of a hurry, I can scan the Sams folder for this - email tbavis(at)rochester(dot)rr(dot)com. .......
270: Tube DIY Asylum, RE: need help with switch nomenclature (0.00)
Posted by Tom Bavis on 2013-12-18, 18:55:39 (67.253.240.216)
I've also seen this type called "alternate action" - two poles change at different positions. But "on-on-on" is most common. .......
271: Tube DIY Asylum, RE: Power Supply Caps (0.00)
Posted by Tom Bavis on 2013-12-17, 11:57:39 (65.202.22.70)
Among other changes, be sure to reduce the 7591 grid resistors. The MAX value per the 7591 data sheet is 300K, and Heath used 470K. If you plan to use modern 7591s, reduce them further (180K-200K). In .......
272: Vintage Asylum, RE: I'm now part of the S5000 club! (0.00)
Posted by Tom Bavis on 2013-12-11, 17:55:14 (67.253.240.216)
5V4 is indirectly heated as well, but rated for 175 mA. The Sams schematic says 100 mA (though that's at idle - it will go higher on audio peaks). You can pick up a lot of 5V4s for the price of a 5AR4 .......
273: Tube DIY Asylum, RE: Yes, he does. (0.00)
Posted by Tom Bavis on 2013-12-06, 06:53:36 (65.202.22.70)
An isolation transformer will NEVER be made with a 1:1 ratio due to losses. Based on the measurements, I would estimate that it's a step-up ratio of 1.02:1. So it's 2% step-up with no load, dropping t .......
274: Tubes Asylum, RE: Knight KN-350 Info needed please. (0.00)
Posted by Tom Bavis on 2013-12-02, 08:15:44 (65.202.22.70)
I looked in the Sams index - KN-350 is not covered. It IS possible that it's another major brand, relabeled. The numbers form the transformers may give a clue. .......
275: Tube DIY Asylum, RE: Capacitor rating for choke input (0.00)
Posted by Tom Bavis on 2013-11-18, 07:46:06 (65.202.22.70)
644V is 460 x 1.4 and that's probably low, since the transformer voltage will be even higher unloaded. I doubt the 550V cap has a high enough surge rating. Use higher voltage or series caps, or delay .......
276: Tube DIY Asylum, RE: Tube socket for 6C33C (0.00)
Posted by Tom Bavis on 2013-11-11, 06:26:34 (65.202.22.70)
I have a few used Johnson sockets if you're interested - tbavis(at)rochester(dot)rr(dot)com .......
277: Vintage Asylum, RE: Fisher P80-C info needed (0.00)
Posted by Tom Bavis on 2013-11-11, 06:17:18 (65.202.22.70)
This is the Fisher manual - I believe the Sams Photofact folder is in my "to be scanned" pile so let me know if you would like it as well. .......
278: Vintage Asylum, RE: Fisher P80-C info needed (0.00)
Posted by Tom Bavis on 2013-11-10, 19:04:36 (67.253.240.216)
If that's the 80-C preamp, I found a copy of the manual with a quick Google search. .......
279: Rocky Road, RE: Americana? (0.00)
Posted by Tom Bavis on 2013-11-09, 15:38:13 (67.253.240.216)
"Tear Stained Letter" made him an honorary American I think... .......
280: Tubes Asylum, RE: 6350: how to test? (0.00)
Posted by Tom Bavis on 2013-10-28, 10:20:53 (65.202.22.70)
The 6463 is similar - don't think there are any others with that pinout. If you can translate the pin connections, it should test about like a 12BH7. .......
281: Vintage Asylum, RE: Very nice... (0.00)
Posted by Tom Bavis on 2013-10-28, 10:17:02 (65.202.22.70)
In case you're looking, sorry - only the G30 made it into Sams. .......
282: Tube DIY Asylum, RE: Fisher 55a is something else. (0.00)
Posted by Tom Bavis on 2013-10-25, 05:36:42 (65.202.22.70)
... people think you lose half of your power with a triode... Not if you can drive the outputs into grid current (class AB2). The cathode follower drivers and 1:1 interstage (with high-frequency coupl .......
283: Tube DIY Asylum, RE: Need help spec'in SS bridge rectifier... (0.00)
Posted by Tom Bavis on 2013-10-23, 17:40:09 (67.253.240.216)
When using a solid state rectifier with choke input, you MUST have some type of snubber to protect the rectifier. A .047 film input cap may be enough, 0.1 uF would be better, with 1200V or higher rati .......
284: Tube DIY Asylum, RE: Start-up with small capacitor...then switch in large capacitor using ground leg as the one switched... (0.00)
Posted by Tom Bavis on 2013-10-23, 17:33:38 (67.253.240.216)
Turn-on inrush current is not the only problem - as input capacitance goes up, peak current goes up as the conduction period goes down. Vacuum rectifiers can only take so much peak current (those peak .......
285: Tube DIY Asylum, RE: One other thing: my power tranny.... (0.00)
Posted by Tom Bavis on 2013-10-17, 14:01:16 (65.202.22.70)
Yes, but only when unloaded. 350 VDC is more realistic under load. If you know the winding resistance it's possible to simulate pretty accurately using PSU Designer from duncanamps.com .......
286: Tubes Asylum, RE: IIRC (0.00)
Posted by Tom Bavis on 2013-10-11, 13:48:16 (65.202.22.70)
Yeah could be relabeled 6211... I had a Realistic "Lifetime" 6V6 that was a relabeled Bendix 5992 - whatever purchasing could find in the surplus outlets once the bigger manufacturers shut down produc .......
287: Tubes Asylum, RE: Am I a Tungar or What am I? (0.00)
Posted by Tom Bavis on 2013-10-11, 13:43:16 (65.202.22.70)
Maybe one of these? .......
288: Tubes Asylum, RE: Ping Tom Bavis (0.00)
Posted by Tom Bavis on 2013-10-01, 07:25:34 (65.202.22.70)
Basically one line of data in the transformer test results: http://www.one-electron.com/Trans_Tests.html P-P parallel 807 in the photo on radiomuseum.com... Triad made some Ampex transformers - both W .......
289: Tubes Asylum, RE: Ampex output (0.00)
Posted by Tom Bavis on 2013-09-27, 18:10:21 (67.253.240.216)
Found it on the One Electron page - 3.4K to 8 Ohms, 7 Hz to 57 KHz, 63 Watts down to 26 Hz... would be pretty good for 6550s or PP-P 6L6s. .......
290: Tubes Asylum, RE: Ampex output (0.00)
Posted by Tom Bavis on 2013-09-26, 16:52:05 (67.253.240.216)
Could be from an early videotape machine - motor was variable frequency, driven by push-pull 6550s... But if secondary is less than an Ohm DCR it may be a speaker winding. .......
291: Tube DIY Asylum, RE: Tube bias (0.00)
Posted by Tom Bavis on 2013-09-25, 06:57:28 (65.202.22.70)
You'd need regulated plate/screen and bias supplies to keep it rock steady. Regulating only one will make current variation worse... as they have have opposite effects (though they don't cancel - cont .......
292: Tube DIY Asylum, RE: Help please (0.00)
Posted by Tom Bavis on 2013-09-12, 18:32:24 (67.253.240.216)
The 300K resistor has zero effect on dynamic range. It's there to reduce the effect of any noise from the pot. The 68K is part of the gain compensation network to stabilize / flatten the closed loop g .......
293: Vintage Asylum, RE: Scott 272 a New Toy. (0.00)
Posted by Tom Bavis on 2013-09-09, 06:52:30 (65.202.22.70)
Mike, email for a scan of the Sams folder - tbavis(at)rochester(dot)rr(dot)com .......
294: Tube DIY Asylum, RE: Maggie 9300 coupling cap options (0.00)
Posted by Tom Bavis on 2013-08-21, 07:16:08 (65.202.22.70)
The two R-C time constants should not be the same with the paraphase inverter. One half of the push-pull drive goes through one stage, the other half goes through two. Typically the inverter stage wil .......
295: Tubes Asylum, RE: what do you know about these tubes that are a 12AT7? (0.00)
Posted by Tom Bavis on 2013-08-20, 06:11:24 (65.202.22.70)
They're closest to a 12AV7, though I think they're more linear... 6414 and 6829 seem to be near-identical, 7062 and 5965 are close. All draw more heater current than a 12AT7. .......
296: Tube DIY Asylum, RE: SE 6BQ5 Motorola amp schematic needed (0.00)
Posted by Tom Bavis on 2013-08-17, 18:05:10 (67.253.240.216)
How about a model or chassis number? Need one or the other to find a schematic. Zfailing that, most any SE schematic should do - values may differ, but there are only so many ways to hook them up... .......
297: Tube DIY Asylum, RE: Coupling, decoupling and bypassing (0.00)
Posted by Tom Bavis on 2013-08-09, 10:47:56 (65.202.22.70)
The power supply (including filtering, bypasses and decoupling) should have a low impedance at all frequencies where the stages have gain... that's up to the megahertz range. Primary reason is stabili .......
298: Tubes Asylum, RE: Can I ask an incredibly stupid Dynaco ST-70 question (0.00)
Posted by Tom Bavis on 2013-08-09, 10:41:42 (65.202.22.70)
It's new, but it's not really a Dynaco Stereo 70. About as close as you can get though... same chassis size, cloned transformers, etc. Others available from Dynakitparts.com, VTA. .......
299: Vintage Asylum, RE: Take a look at this amp I picked up on Ebay for a 130 dollars. (0.00)
Posted by Tom Bavis on 2013-08-09, 10:28:47 (65.202.22.70)
Calrad SA-30. I had the "A" or "B" version which didn't have those nice potted transformers. I think Olson sold this under their own brand, probably sold under other names too. I have a scan of the Sa .......
300: Tube DIY Asylum, RE: Advantages? (0.00)
Posted by Tom Bavis on 2013-08-01, 13:38:56 (65.202.22.70)
The engineers at Maganvox must have thought there was an advantage to using only one output tube number. They used two, four, six, or eight per amp. Sixteen 6V6s in the Concert Grand console. (six PPP .......
301: Tube DIY Asylum, RE: Manley Sting-Ray (0.00)
Posted by Tom Bavis on 2013-08-01, 13:27:04 (65.202.22.70)
They claim 40W in UL, 20 in triode. Both a bit optimistic in my humble opinion... .......
302: Tubes Asylum, RE: Magic Eye Tube (0.00)
Posted by Tom Bavis on 2013-07-31, 11:52:22 (65.202.22.70)
Never made in the US to my knowledge. All I've seen are European. .......
303: Vintage Asylum, RE: Pilot 254 Receiver, fixing need help (0.00)
Posted by Tom Bavis on 2013-07-31, 11:48:55 (65.202.22.70)
Sams MHF-94 - check with Bob at findatube.com or Google it - I found a copy for $6.99. .......
304: Tube DIY Asylum, RE: The Output transformers are likely saturating. (0.00)
Posted by Tom Bavis on 2013-07-25, 13:26:40 (65.202.22.70)
Agreed - check the idle current in the output tubes. Get a matched set at the drugstore for $10... just set the wayback machine for 1965... .......
305: Vintage Asylum, RE: Finding noise with a scope (0.00)
Posted by Tom Bavis on 2013-07-24, 06:59:53 (65.202.22.70)
Signal levels are pretty low in a phono preamp - I wouldn't expect to see anything useful on a 'scope. No carbon comp resistors, I hope... metal film will have least noise. Does DC heater supply have .......
306: Vintage Asylum, RE: Why bother? (0.00)
Posted by Tom Bavis on 2013-07-24, 06:49:37 (65.202.22.70)
Bogen had a lot of models, so it's hard to generalize... some were very good. Those of us who build amps might be interested in which output transformers from "cheap PA" amps are better than anything .......
307: Tube DIY Asylum, RE: Source for tube socket covers (0.00)
Posted by Tom Bavis on 2013-07-22, 12:44:16 (65.202.22.70)
DigiKey has a few in stock, 1", 3/4", 7/8" - search "hole plug", "hardware", "in stock", Mouser might but they don't show up in a quick search. Allied has them too... .......
308: Tubes Asylum, RE: Origin of the 6L6GC? (0.00)
Posted by Tom Bavis on 2013-07-22, 12:29:50 (65.202.22.70)
"Tube Lore" lists the registration date for each number, but doesn't indicate what company registered it. 7027 came first (3-58), then 6L6GC (11-58), and 7581 was registered in 1959. .......
309: Tubes Asylum, RE: Can 6k6 replace the 6v6... (0.00)
Posted by Tom Bavis on 2013-07-19, 18:42:47 (67.253.240.216)
Cathode bias resistor will need to be increased, or it will cook... needs more negative grid bias for the same operating point. And it won't take a lot of B+ voltage. So I wouldn't call it plug 'n pla .......
310: Vintage Asylum, RE: Bogen AP-35 Loudness circuit (0.00)
Posted by Tom Bavis on 2013-07-12, 08:40:28 (65.202.22.70)
Shorting the .01s is probably the best way to disable it - removing both the cap and resistor may make the volume control action a bit abrupt. The 68 pF may help compensate for the Miller effect rollo .......
311: Tube DIY Asylum, RE: Ampex 6973 mod question... Eli? (0.00)
Posted by Tom Bavis on 2013-06-18, 14:09:08 (65.202.22.70)
C1, C2 seem small to me, but I haven't gone through the numbers. With a CCS, the two loads on the diff stage should be equal. C7 gives some low-frequency boost, probably EQ for the particular speaker( .......
312: Vintage Asylum, RE: AC transformer for Janszen I-30 (0.00)
Posted by Tom Bavis on 2013-05-24, 07:53:09 (65.202.22.70)
Reversing a lower-voltage transformer won't work, since the higher flux in the core will cause it to saturate. Hammond 260A is 400VCT, 40 mA (so it will probably be a bit higher at near zero load. It .......
313: Tubes Asylum, RE: ** Thanks, guys *** (0.00)
Posted by Tom Bavis on 2013-05-13, 06:57:15 (65.202.22.70)
Tan base ones ARE early Westinghouse, regardless of whose name is on 'em... .......
314: Tubes Asylum, RE: B&K 707 and soldering Type 55 bulbs (0.00)
Posted by Tom Bavis on 2013-05-13, 06:55:31 (65.202.22.70)
I think the center contact is an eyelet - so you can solder a wire to the bulb, thread it trough the hole, and solder it to the terminal. Notice that said I _think_... I haven't opened up my 707 to do .......
315: Tubes Asylum, RE: What's a 1684? (some IBM tube) (0.00)
Posted by Tom Bavis on 2013-05-02, 17:04:31 (67.253.240.216)
Jim Cross has a little more info: .......
316: Tube DIY Asylum, RE: What about parallel connections on common toroids? (0.00)
Posted by Tom Bavis on 2013-04-17, 19:25:43 (67.253.240.216)
If the unloaded primary current doesn't increase when they are connected in parallel, the secondaries are exactly equal in voltage. With equal number of turns and the same wire length, no derating wou .......
317: Tube DIY Asylum, 12BY7 (0.00)
Posted by Tom Bavis on 2013-04-14, 11:42:06 (67.253.240.216)
12HL7, 12GN7, 12HG7, 11HM7 are even higher transconductance (20-30 mA/V) in the same base. The closest equivalents 12DQ7 and 12BV7 are not common, usually they are dual or triple marked (like 12BV7/12 .......
318: Vintage Asylum, RE: Lafayette tuner --pilot light (0.00)
Posted by Tom Bavis on 2013-04-14, 11:03:48 (67.253.240.216)
If it's a screw base, #40. If bayonet, #47. Radio Shack should have them. .......
319: Tube DIY Asylum, RE: Determining P to P impedance in an unknown OPT (0.00)
Posted by Tom Bavis on 2013-04-03, 07:17:35 (65.202.22.70)
Here's an example: 24V on primary, measure 0.80V and 0.56V on secondary taps. Ratio is 30 : 1 and 42.8 : 1 Impedance ratios are 900:1 and 1836:1 So it's 7.2K:8, 7.3K:4 (14.4K to 16 is unlikely...) The .......
320: Tubes Asylum, RE: EZ90 for EZ80 in AMR 77.1? (0.00)
Posted by Tom Bavis on 2013-03-29, 13:12:12 (65.202.22.70)
EZ90 is a 7-pin, EZ80 is a 9-pin. EZ81 will sub if the unit can supply the extra heater current (and there's room for the extra height). .......
321: Tubes Asylum, RE: can you help identify this tube? (0.00)
Posted by Tom Bavis on 2013-03-20, 09:24:23 (65.202.22.70)
* code is Amperex, Long Island plant. .......
322: Rocky Road, RE: Actually, those 3 sell massive amounts of tunes as well as get critical praise from old and new reviewers and (0.00)
Posted by Tom Bavis on 2013-03-15, 11:29:28 (65.202.22.70)
Oasis... if the radio doesn't have station buttons, the OFF button will do - can't stand 'em! Wilco... I've liked few tracks I've heard, but could not listen to "A Ghost is Born" more than once. Maybe .......
323: Vintage Asylum, RE: Does anyone recognize this amp ot wjay brand it might be. (0.00)
Posted by Tom Bavis on 2013-03-14, 13:07:37 (65.202.22.70)
Pederson W-50. See my web page for the Sams folder: .......
324: Tube DIY Asylum, RE: Interesting idea. (0.00)
Posted by Tom Bavis on 2013-03-04, 14:30:13 (65.202.22.70)
No, there won't be any frequencies below the repetition rate - what IS there is a phase difference in the harmonics. If the harmonic levels and phase match the original. so does the waveform. If some .......
325: Vintage Asylum, RE: Scott 399 receiver service manual (0.00)
Posted by Tom Bavis on 2013-02-05, 06:01:44 (65.202.22.70)
Sams Photofact index says it's in folder 526-8 - not in my files but shouldn't be too hard to turn up. Steve Johnson probably has it: .......
326: Tube DIY Asylum, RE: Has anybody ever tried 6360? (0.00)
Posted by Tom Bavis on 2013-02-04, 07:11:45 (65.202.22.70)
Seems like a possible replacement for ELL80 / 6HU8 in a German radio (at least one that doesn't use a printed circuit board...). .......
327: Vintage Asylum, RE: Stromberg Carlson SAU-22 transformer (0.00)
Posted by Tom Bavis on 2013-01-06, 08:08:17 (67.253.240.216)
Idle current in the 6BQ5s is 80 mA total, so amp might be 90 mA altogether. 125 mA is plenty of margin. But your B+ will be about 400V with that Stancor, so I'd look for one a little lower in voltage. .......
328: Vintage Asylum, RE: Stromberg Carlson SAU-22 transformer (0.00)
Posted by Tom Bavis on 2013-01-05, 19:57:28 (67.253.240.216)
I'd go for a little lower voltage, though you can add a series resistor if it's too high. Don't want it any taller if you have a cage... if that Stancor is the same size it's a pretty good choice. ::: .......
329: Tubes Asylum, RE: Those Smoked Glass RCA 6SN7's... (0.00)
Posted by Tom Bavis on 2013-01-04, 06:33:20 (65.202.22.70)
6SL7 mismarked as 6SN7? 6SL7 would definitely test lower. I have a Realistic 12AU7 that's mis-labeled 12AX7 on the glass and on the box... a (probable) 6CB6 mis-labled as 6BJ6... .......
330: Vintage Asylum, RE: rewire to 6U8/6GH8 (0.00)
Posted by Tom Bavis on 2013-01-03, 07:15:15 (65.202.22.70)
I have a few amps in the queue which call for 7199. I have 6 7199s, about 600 in the 6U8 footprint - I know which ones _I'll_ use... One data point: in a Stromberg ASR-120, a pair of 6GH8s biased up t .......
331: Vintage Asylum, RE: tube amp speaker hookup help needed (0.00)
Posted by Tom Bavis on 2012-12-30, 19:05:00 (67.253.240.216)
Looks like "C" (common) on top, then "1" then "2" at bottom. Connections look right to me. .......
332: Vintage Asylum, RE: Yamaha CA-1010 excessive leakage current? (0.00)
Posted by Tom Bavis on 2012-12-25, 09:35:04 (67.253.240.216)
Voltage alone doesn't mean much - if it did, the 14,000V charge you develop shuffling across the living room rug would be lethal rather than an annoying ZAP. What matters is current. 1 mA is considere .......
333: Tube DIY Asylum, RE: Power transformer spec query (0.00)
Posted by Tom Bavis on 2012-12-17, 06:18:06 (65.202.22.70)
Sounds like it's only good for the rated 80 mA. I have found SOME transformers that weer good for nearly twice the marked current - but not this one. My analysis: the power dissipation in the winding .......
334: Tube DIY Asylum, RE: Power transformer spec query (0.00)
Posted by Tom Bavis on 2012-12-12, 09:33:01 (65.202.22.70)
Measure the DC resistance of the HV winding and post your result. There MAY be a bit more capacity available. .......
335: Tube DIY Asylum, RE: Vintage STACO VARIAC [Model #: 3PN1010]: HOW TO REMOVE TOP CAP/DIAL? (0.00)
Posted by Tom Bavis on 2012-12-03, 10:51:17 (65.202.22.70)
The setscrews will be slotted screws or hex Allen Head (probably 5/64" or 3/32" (I wouldn't expect metric). They'd be VERY hard to strip, but if so, I suppose they could be removed with a drill and le .......
336: Tubes Asylum, RE: Stupid Tube Tester Calibration Question (0.00)
Posted by Tom Bavis on 2012-11-28, 10:01:53 (65.202.22.70)
Doesn't matter what scale the Fluke is on - its an 11 megohm load regardless of range. So you have to select a range appropriate for the voltage to be measured, and a corresponding load. TYPICALLY the .......
337: Tube DIY Asylum, RE: That worked! (0.00)
Posted by Tom Bavis on 2012-11-12, 06:11:00 (65.202.22.70)
See if that cap heats noticeably... it could be carrying an amp or more... PSUD can give an idea of the current. .......
338: Tube DIY Asylum, RE: fixed bias for PP KT88 questions (0.00)
Posted by Tom Bavis on 2012-11-02, 06:16:04 (65.202.22.70)
If you have an isolated transformer winding for bias, of course use a full-wave bridge. With a tap on another winding, you're stuck with half-wave, so a bit more filtering is required. .......
339: Tubes Asylum, RE: Where (best) to use Carbon Resistors? (0.00)
Posted by Tom Bavis on 2012-10-29, 05:52:36 (65.202.22.70)
Amount of heat will be the same regardless of type or size of resistor. TEMPERATURE of larger parts will be lower. .......
340: Tube DIY Asylum, RE: power supply (0.00)
Posted by Tom Bavis on 2012-10-24, 06:53:15 (65.202.22.70)
For the 90V, you might start with a 120V isolation transformer - Triad has a 50VA part that's only about $15 or so. For the 1.5V, I'd use a switching regulator - National has a number of parts that wi .......
341: Tubes Asylum, RE: Just outta curiosity (0.00)
Posted by Tom Bavis on 2012-10-21, 08:49:00 (67.253.240.216)
RCA did a lot of the early tube development and first used 5V for tubes that were made to be run on 6.3V batteries. Radios used filament rheostats which were adjusted as the battery voltage dropped, t .......
342: Tubes Asylum, RE: Pilot 232 with 4-8-16 output wired different than schematic of 8 -16 output? (0.00)
Posted by Tom Bavis on 2012-10-13, 13:09:22 (67.253.240.216)
According to the Sams folder, the 8-16 Ohm output transformer is Pilot part number 55-59. Other Pilot part numbers have a similar format. .......
343: Tubes Asylum, RE: Pilot 232 with 4-8-16 output wired different than schematic of 8 -16 output? (0.00)
Posted by Tom Bavis on 2012-10-11, 11:45:39 (65.202.22.70)
Sounds like the secondary phase was reversed when the 4 Ohm tap was added. So the feedback had to come from the opposite end, with a lower value resistor since it's a lower voltage. Grounding the 4 Oh .......
344: Tube DIY Asylum, RE: Found it (0.00)
Posted by Tom Bavis on 2012-10-10, 06:40:29 (65.202.22.70)
I haven't measured that part number. Typical big Tek transformer has multiple windings at 120-150V, each about 3 Ohms. So you can get a 400V, 9 Ohm secondary by connecting 'em in series. With FWB, goo .......
345: Tube DIY Asylum, RE: Power transformer from and old Tektronix tube oscilloscope (0.00)
Posted by Tom Bavis on 2012-10-09, 17:21:11 (67.253.240.216)
Part number? I have a few of them mapped out... .......
346: Vintage Asylum, RE: Sherwood S5000 mk2 [7591] (0.00)
Posted by Tom Bavis on 2012-10-09, 17:20:09 (67.253.240.216)
I have the Sams folder for the S-5000II - shows 7591 - email tbavis(at)rochester(dot)rr(dot)com .......
347: Tube DIY Asylum, RE: 112w pushpull 6lf6 (0.00)
Posted by Tom Bavis on 2012-10-09, 09:09:02 (65.202.22.70)
Is the 6J5 run parafeed as Maganvox used it? I wonder how much DC it cabn take... .......
348: Tubes Asylum, RE: Tube Rectifiers - Need Expert Help (0.00)
Posted by Tom Bavis on 2012-09-24, 06:09:31 (65.202.22.70)
5U4 draws 50% more heater current than the others, so don't try it unless you're sure the transformer can take it. Add 5V4 to your list - same as GZ32, really. Expect to rebias since different tubes .......
349: Tube DIY Asylum, RE: 6973 to 7189 conversion besides the pinout what else? (0.00)
Posted by Tom Bavis on 2012-09-21, 09:59:30 (65.202.22.70)
6CZ5s may be OK if the screen voltage isn't too high and the grid resistors are reduced to 100K (6973 allows up to 500K in fixed bias). May be a good idea to reduce the grid resistors anyway... For in .......
350: Tube DIY Asylum, RE: Resistor dissipation Question (0.00)
Posted by Tom Bavis on 2012-09-17, 09:07:04 (65.202.22.70)
An important fact that nobody has mentioned... the RMS current through this resistor is considerably higher than the total DC current! The current waveform here is not a sine wave - it has a higher pe .......
351: Tube DIY Asylum, RE: How to determine a power transformer's current capability (0.00)
Posted by Tom Bavis on 2012-09-14, 07:51:23 (65.202.22.70)
Core loss is minor - winding resistance is the major factor determining losses which cause the temperature rise. As has been mentioned, insulation varies, and modern parts can probably work at a highe .......
352: Tubes Asylum, RE: EL84 pinout query (0.00)
Posted by Tom Bavis on 2012-09-04, 14:06:21 (65.202.22.70)
Don't use those "IC" pins. Connections vary by maker and vintage... .......
353: Tube DIY Asylum, Audiophool is Dead, long live Audiophool! (0.00)
Posted by Tom Bavis on 2012-08-27, 14:11:05 (65.202.22.70)
My web site, formerly found at audiophool.cjb.net, can now be found at audiophool.com - if I can get in contact with CJB.net, maybe I can find out what happened, and perhaps I can revive the old URL f .......
354: Tubes Asylum, RE: Source for 10EM7's (0.00)
Posted by Tom Bavis on 2012-08-17, 13:46:28 (65.202.22.70)
There's nothing BUT NOS after all... most sellers will pick out your choice of brand for you for a few bucks extra... Bob Dobush's site below says "add 20% for brand preference"... Still, it's not a t .......
355: Tube DIY Asylum, RE: Elecrolytic capacitor reforming (0.00)
Posted by Tom Bavis on 2012-08-17, 13:36:24 (65.202.22.70)
Less than 1 mA should be OK - it represents less than a half-watt dissipation at 450V. I WOULD be concerned if you see any jumps in current after it has stabilized. Still no guarantee that they won't .......
356: Tube DIY Asylum, RE: common cathode 6x8 (0.00)
Posted by Tom Bavis on 2012-08-10, 09:16:36 (65.202.22.70)
Fred Nachbauer (if he hasn't been sainted yet, he should be...) published this circuit using the 6X8... .......
357: Tube DIY Asylum, RE: triad R-14A (0.00)
Posted by Tom Bavis on 2012-07-19, 19:02:24 (67.253.240.216)
Triad used the usual color code on all their transformers I've seen, and printed a diagram on the side besides...... Blk: primary Red & Red/Yel: HV&CT Yel: 5V rectifier heater Grn & Grn/Yel: heater&C .......
358: Tube DIY Asylum, RE: Reducing wattage on Stromberg-Carlson asr433 (0.00)
Posted by Tom Bavis on 2012-07-13, 05:57:08 (65.202.22.70)
You can measure the idle current by measuring the drop across the cathode resistor and dividing by resistance (Good 'ol Ohm's law). Multiply that by the plate voltage minus the cathode voltage to get .......
359: Vintage Asylum, RE: All for want of a fuse-holder cap! (HK 800+ rcvr) (0.00)
Posted by Tom Bavis on 2012-07-02, 17:01:15 (67.253.240.216)
Email with your address and one will go out tomorrow. Fits the H-K 730 and Marantz 4240, which happened to be nearby. There's also a style with the same thread, but shorter threaded section and no spr .......
360: Vintage Asylum, RE: All for want of a fuse-holder cap! (HK 800+ rcvr) (0.00)
Posted by Tom Bavis on 2012-07-01, 19:38:39 (67.253.240.216)
If you don't have one yet, I'm sure my junk box will yield one. In fact, I think I just pulled one from a junker Kenwood today... tbavis(at)rochester(dot)rr(dot)com .......
361: Tube DIY Asylum, RE: 5BC3 rectifier (0.00)
Posted by Tom Bavis on 2012-06-27, 11:11:33 (65.202.22.70)
Pretty much a re-based 5U4GB. RCA was pushing their own latest tubes, Novar base 5BC3 and 7868, and the 7199. .......
362: Tube DIY Asylum, RE: ok, so... (0.00)
Posted by Tom Bavis on 2012-06-22, 09:13:52 (65.202.22.70)
Ground is irrelevant as far as output voltage. You'll get 9V unloaded, but it will drop under load. How MUCH it will drop will depend on transformer and other losses. Due to the "peaky" distorted c .......
363: Vintage Asylum, RE: Anyone Recognize this Amp? (0.00)
Posted by Tom Bavis on 2012-06-19, 13:00:20 (65.202.22.70)
It's cool, whatever it is... I think the logo plate wore off... The "M-R" tube was wartime manufacture, "Maintenance/Repair" only, since there was no civilian electronics being made (some was made, be .......
364: Vintage Asylum, RE: Arkay SA-25 Stereo-Binaural amp (0.00)
Posted by Tom Bavis on 2012-06-15, 11:20:50 (65.202.22.70)
Schematic is in Sams Photofacts #599-Servicer, dated 1962,so it's earlier than that... I would have guessed late '50s. .......
365: Tube DIY Asylum, RE: Un-readable on my macbook pro: A circuit designed by Richard Burwen (0.00)
Posted by Tom Bavis on 2012-05-23, 06:14:07 (65.202.22.70)
DjVu versions on my web page below. You'll need the DjVu plug-in (half a dozen available for Windows and a couple for Android so there must be something for the Mac...) .......
366: Tube DIY Asylum, RE: combination resistor/choke anode load (0.00)
Posted by Tom Bavis on 2012-05-22, 10:59:33 (65.202.22.70)
To first order, circuit is same. Shunt capacitance, from choke winding to core will have a reduced effect if the choke is in the ground end of the series circuit, giving a more gradual high frequency .......
367: Tubes Asylum, RE: Fisher X-101-B (0.00)
Posted by Tom Bavis on 2012-05-22, 10:51:52 (65.202.22.70)
I have a scan of the Sams folder. email tbavis(at)rochester(dot)rr(dot)com .......
368: Tubes Asylum, RE: 6BM8 - Replacements or Substitutions? (0.00)
Posted by Tom Bavis on 2012-05-10, 07:54:59 (65.202.22.70)
Russian 6F3P is probably the tube they came with... NOS 6BM8s are available, of US, Euro, probably Japan and Korea manufacure... I believe you will need matched pairs for these amps. I DID find one tu .......
369: Tube DIY Asylum, RE: why do caps motorboat (0.00)
Posted by Tom Bavis on 2012-05-07, 06:55:08 (65.202.22.70)
Supply has plenty of filtering for hum, but a high output impedance. This means that the voltage will sag as the output stage draws current, which is fed to earlier stages. Try adding some more output .......
370: Tube DIY Asylum, RE: through bolts (0.00)
Posted by Tom Bavis on 2012-05-01, 06:03:15 (65.202.22.70)
Mounting bolts can form a shorted turn that intercepts part of the magnetic flux, wasting power as heat in a power transformer, reducing inductance (and low-end response) in an output transformer. The .......
371: Tube DIY Asylum, RE: replacing stamped transformer bells with solid aluminum (0.00)
Posted by Tom Bavis on 2012-04-29, 19:58:36 (67.253.240.216)
Some LONG studs... alignment will be tricky. Female threaded inserts could be used - or just tap the aluminum if it's thick enough. Remember that the bolts should be insulated - cover them with shrink .......
372: Tube DIY Asylum, RE: How do you determine when the Choke get to magnetic saturation (0.00)
Posted by Tom Bavis on 2012-04-28, 17:12:15 (67.253.240.216)
How big is this choke? 300 mA in 100 Ohms is nine watts, which is a lot to dissipate in a choke (though a big enough one could handle it...). Consider too, that the choke will go up in resistance as i .......
373: Vintage Asylum, RE: Your thoughts on this Stromburg Carlson set up (0.00)
Posted by Tom Bavis on 2012-04-28, 16:54:30 (67.253.240.216)
ASR-333 or more likely 433 amp, (433 has mag phono / tape head preamp, 333 can take only ceramic cartridge). SR-445 tuner. "Simulcast" stereo only - before multiplex, the only way to broadcast stereo .......
374: Tube DIY Asylum, RE: 500MA NSTALLED IN 200MA CIRCUITS (0.00)
Posted by Tom Bavis on 2012-04-16, 17:06:52 (67.253.240.216)
The classic Williamson circuit with 807s... A very good output transformer is required, but there are ways to compensate for a lessor one, such as reducing global feedback and adding some local feedba .......
375: Tube DIY Asylum, RE: 500MA NSTALLED IN 200MA CIRCUITS (0.00)
Posted by Tom Bavis on 2012-04-15, 17:59:08 (67.253.240.216)
Yes, it'll be fine. Voltage will be a little higher under the light load. If you're using a tube rectifier, you may need to add some resistance in series to limit peak current, depending on capacitor .......
376: Tubes Asylum, RE: PP 6V6 triode = 15 wpc ??? (0.00)
Posted by Tom Bavis on 2012-03-29, 05:27:33 (65.202.22.70)
Even the rating of 5W at 1% distortion is questionable to me... 6V6 data sheet says 3.3W in class A, 4.75W in AB for push-pull triode on 300V supply - distortion isn't given, but power is usually spec .......
377: Tube DIY Asylum, RE: Resistor ratings question (0.00)
Posted by Tom Bavis on 2012-03-28, 13:13:27 (65.202.22.70)
Check again... dielectric working voltage is 1500VAC. Should be adequate... .......
378: Vintage Asylum, RE: Pinging Tom Bavis - Stromberg Carlson Advice Needed. (0.00)
Posted by Tom Bavis on 2012-03-24, 14:39:37 (67.253.240.216)
I probably have a control that would work - assuming it IS the control (an ohmmeter would tell you). Could also be a tube or other part in the left channel, or even a bad solder connection. I'll measu .......
379: Tubes Asylum, RE: Any 7 Pin Equivalent to 6SN7? (0.00)
Posted by Tom Bavis on 2012-03-11, 13:32:25 (67.253.240.216)
As mentioned, not enough pins unless it has a common cathode. E90CC (5920) has a mu of 27, Transconductance about double that of the 6SN7. Common cathode of course - same pinout as 6J6. .......
380: Tube DIY Asylum, RE: dropping AC voltage with a capacitor (0.00)
Posted by Tom Bavis on 2012-03-07, 06:32:01 (65.202.22.70)
Why not rectify it (about 28vdc) and connect heaters in series? You'll probably need a dropping resistor to get 24VDC (may not be enough extra voltage to regulate at 24VDC...). Or use a switching regu .......
381: Tubes Asylum, RE: equivalentes for 274A (0.00)
Posted by Tom Bavis on 2012-03-02, 07:56:18 (65.202.22.70)
A preamp isn't likely to need anywhere remotely close to the 225 mA rating of the 274A. An 80 (which is rated for 125 mA) should be a perfectly good substitute. The 5Z3 needs 3A for the heater vs. 2A .......
382: Tube DIY Asylum, RE: 12bh7 substitution in pilot sa 260 (0.00)
Posted by Tom Bavis on 2012-02-27, 08:14:14 (65.202.22.70)
5AR4 has a lower voltage drop than 5U4, so voltage will increase. 5R4 will decrease voltage - a safer approach. .......
383: Tube DIY Asylum, RE: 6BQ5 Plate Voltage questions on Heathkit conversion to guitar head (0.00)
Posted by Tom Bavis on 2012-02-18, 17:45:26 (67.253.240.216)
The tube's screen grids get a real beating in a guitar amp - add some 470 Ohm droppping resistors in each screen lead (from screen to transformer if it's still in UL). You'll find these in most guitar .......
384: Vintage Asylum, RE: Thordarson 2A3 amplifier Literature (0.00)
Posted by Tom Bavis on 2012-02-09, 06:14:08 (65.202.22.70)
I assume you've looked through the Thordarson literature on my site? Looks like I may need to fix a link for the Tru-Fidelity catalog though... .......
385: Tubes Asylum, RE: why is this tube drawing so much current? (0.00)
Posted by Tom Bavis on 2012-02-08, 13:19:55 (65.202.22.70)
Perhaps the circuit was "corrected" to match the incorrect schematic? That's the AFC tube, it's possible it NEVER worked... I can email the Bogen TP-50 tuner schematic, which might show how it SHOULD .......
386: Tubes Asylum, RE: Also can the 6SN7 be used as a substitue? (0.00)
Posted by Tom Bavis on 2012-02-06, 08:55:36 (65.202.22.70)
No, 6SN7 is a dual triode, 6SJ7 is a pentode. Nothing alike about 'em. I probably have six metal 6SJ7s for every glass one... metal was more common as 6SJ7 was typically used as a low-level amplifier, .......
387: Tube DIY Asylum, RE: Are Axon caps know for picking up hum? (0.00)
Posted by Tom Bavis on 2012-02-02, 08:57:56 (65.202.22.70)
The only factors that would affect hum pickup are surface area of the cap and distance from AC voltage (strength of E-field). If there's hum pickup, repositioning or shielding will help. (and if there .......
388: Vintage Asylum, RE: Besides Radio Shack or EBAY where can a person.. (0.00)
Posted by Tom Bavis on 2012-01-18, 17:47:32 (67.253.240.216)
Your email link seems to be bad - you can contact me at tbavis(at)rochester(dot)rr(dot)com. .......
389: Tube DIY Asylum, RE: 6KG6 (0.00)
Posted by Tom Bavis on 2012-01-17, 07:09:24 (65.202.22.70)
Have you seen this one? .......
390: Tubes Asylum, RE: Need help understanding what to look for in finding a 1 : 1 / 1X direct probe for a Sencore SC61 (0.00)
Posted by Tom Bavis on 2012-01-17, 07:05:47 (65.202.22.70)
10X probes have a range of inputs that can be compensated - 1 meg / 30 pF is a typical scope input. Has nothing to do with probe tip capacitance. The voltage divider in the tip isolates the cable capa .......
391: Tube DIY Asylum, RE: Using Power Trannys Rated Over 60cps? (0.00)
Posted by Tom Bavis on 2012-01-17, 06:50:34 (65.202.22.70)
Sure you can use them! Just don't exceed 18 VAC with 60 Hz on the primary... Pssst... anybody want to buy a 400 Hz Variac? Guess there WAS a reason that it was free... Actually I'll probably keep it f .......
392: Vintage Asylum, RE: Besides Radio Shack or EBAY where can a person.. (0.00)
Posted by Tom Bavis on 2012-01-17, 06:34:48 (65.202.22.70)
I can check my basement stock - let me know diameter, length, number of sections, bottom thread (usually 3mm). .......
393: Vintage Asylum, RE: help with audio transformers (0.00)
Posted by Tom Bavis on 2012-01-15, 09:13:21 (67.253.240.216)
UTC A-18 brings $50 - 100 on eBay. The LS-60A is an output transformer, 4600 Ohms to various speaker impedances, 30W, 20-20 KHz. I'd expect it to bring a few hundred. I don't recognize the Chicago num .......
394: Tube DIY Asylum, RE: Why hybrid power supply?? (0.00)
Posted by Tom Bavis on 2012-01-11, 13:19:24 (65.202.22.70)
No, the inrush current and peak repetitive current limits for the rectifier should still be observed. These can be simulated using Duncan Amps PSU designer (simulate using an all-tube FWB and a solid- .......
395: Vintage Asylum, RE: Knight KG-240 Schematic (0.00)
Posted by Tom Bavis on 2012-01-11, 13:04:05 (65.202.22.70)
6GW8s have gotten scarce, but there are other possible choices for tubes - 6BM8 is probably the closest, and they're easier to find. Transformers would run close to $200 though... I have one of these .......
396: Vintage Asylum, RE: Ampex audio control center 402 transformer replacement (0.00)
Posted by Tom Bavis on 2011-12-29, 18:50:20 (67.253.240.216)
The Dyna transformer will do nicely - but it will use a full-wave center-tap rectifier instead of a voltage doubler. Heater supply would best be a full-wave bridge - and a series resistor will probabl .......
397: Tubes Asylum, RE: Measuring true Gm with Knight 600B? (0.00)
Posted by Tom Bavis on 2011-12-23, 15:15:45 (67.253.240.216)
Knight 800 is an emission tester - basically tests all tubes as diodes. Cathode emission drops with age and use, as does transconductance, though not necessarily proportionately. And of course, is of .......
398: Vintage Asylum, RE: Schematic or Sams folder needed please (0.00)
Posted by Tom Bavis on 2011-12-21, 07:46:29 (67.253.240.216)
Does it look like the model 29? See below. If so I have a scan - tbavis(at)rochester(dot)rr(dot)com .......
399: Tubes Asylum, RE: Seeking linear triode (0.00)
Posted by Tom Bavis on 2011-12-17, 19:27:04 (67.253.240.216)
12B4 curves look pretty good to me... You might look at 6AH4, 6CK4. Or parallel the sections in a 6BX7... .......
400: Vintage Asylum, RE: Tweeter update (0.00)
Posted by Tom Bavis on 2011-12-16, 17:38:52 (67.253.240.216)
One resistor will work, but it will shift the crossover frequency a little lower. Two resistor pad will keep the same impedance, same frequency. .......
401: Vintage Asylum, RE: Freed Eisemann 910 amp (0.00)
Posted by Tom Bavis on 2011-12-16, 17:35:20 (67.253.240.216)
Don't know the Freed-Eisemann, but the Bell amp is in Sams folder 285-2, 1955. Don't think I have that one, but I'll look. .......
402: Tubes Asylum, RE: Sovtek 6SC7 (0.00)
Posted by Tom Bavis on 2011-12-16, 08:55:04 (65.202.22.70)
For what it's worth, the 6SC7 is identical to 6SL7 except for pinout - if it's used in a differential stage or with cathode grounded (as with grid-leak bias) either one can be used. .......
403: Tube DIY Asylum, RE: How likely is it that an OPT from Triode El has miscolored secondaries (0.00)
Posted by Tom Bavis on 2011-12-01, 11:40:20 (65.202.22.70)
There's no standard for polarity of audio transformers - so you may have to reverse the secondary. This can be a pain if there's more than one output tap, as the common terminal is no longer ground. I .......
404: Tube DIY Asylum, RE: Steel leads (0.00)
Posted by Tom Bavis on 2011-11-30, 10:37:25 (65.202.22.70)
In my other life, I came across a batch of .01 Ohm 7W resistors with steel leads... since they're 4-terminal (Kelvin connection), they gave an accurate current sample reading, but they were dissipatin .......
405: Tube DIY Asylum, RE: Cree diodes and heatsinking (0.00)
Posted by Tom Bavis on 2011-11-25, 14:29:57 (67.253.240.216)
They'll be dissipating about 1/4W each - no heatsink required. .......
406: Tube DIY Asylum, RE: Exact equivalent (multiple tubes OK) for 7199? (0.00)
Posted by Tom Bavis on 2011-11-19, 10:45:05 (67.253.240.216)
The 7687 is specified to be same as the the 7199 but in the 6U8/6GH8 pinout. Probably much rarer than 7199 though... .......
407: Tubes Asylum, RE: about U.S. version e80cc/6085. (0.00)
Posted by Tom Bavis on 2011-11-03, 06:36:18 (65.202.22.70)
Looks like 6829 or 6414 - these are close equivalent to 6085. .......
408: Tubes Asylum, RE: Is there a noval single triode equivalent for a 6DJ8 / noval half of a 6CG/FQ7? (0.00)
Posted by Tom Bavis on 2011-11-01, 06:57:52 (65.202.22.70)
12AU7 would be close to half a 6CG7 if the sections are paralleled. 6DL4 is probably closest to half a 6DJ8. 12A4 is close to 2 6CG7 halves in parallel. .......
409: Tube DIY Asylum, RE: Need a probe for Sencore SC61/3080 part # 39G294 (0.00)
Posted by Tom Bavis on 2011-10-20, 07:31:47 (65.202.22.70)
Good luck as they're unique to Sencore... and there always to be more 'scopes than probes... You may know this, but it might of interest to others... the probes are special, having two voltage divider .......
410: Tubes Asylum, RE: USA Amperex 6922 - strange label (0.00)
Posted by Tom Bavis on 2011-10-11, 07:12:17 (65.202.22.70)
Polarad made test equipment - I'm not surprised that they used Amperex tubes. The etched code near the bottom should start with * (asterisk) if it was made in the Amperex Long Island plant. ::: TOPIC: .......
411: Vintage Asylum, RE: Output tubes for a Fisher 500 mono receiver... (0.00)
Posted by Tom Bavis on 2011-10-05, 09:05:35 (65.202.22.70)
Later 500s used 5881 - it was screened on the chassis. .......
412: Tube DIY Asylum, RE: How long can lytics sit around and still be usable? (0.00)
Posted by Tom Bavis on 2011-09-27, 06:45:49 (65.202.22.70)
1000 hours is the life at maximum voltage, temperature and ripple current. Multiply by 2 for every 10 deg C reduction in temperature. So a 105C cap at 45C (113F) is 64,000 hours - 8 years of use. More .......
413: Tubes Asylum, RE: Replacement for 6F2 preamp tube for my Xindak (0.00)
Posted by Tom Bavis on 2011-09-22, 05:38:25 (65.116.131.6)
6F2 appears to be a Chinese (only) number. I have found references to ECF82 (6U8) being an equivalent. 6GH8, 6EA8, 6KD8, 6678 are all close subs for 6U8. .......
414: Vintage Asylum, RE: HELP with Oil Capacitor for Marantz Five Mono Tube Amps (0.00)
Posted by Tom Bavis on 2011-09-17, 13:37:31 (69.205.116.106)
I have a single one, 6 uF @ 600V, but it's 4 1/4" (about 108 mm) tall. Close enough? Perhaps I can turn up another one. .......
415: Vintage Asylum, RE: Help with Fisher restoration kits (0.00)
Posted by Tom Bavis on 2011-08-17, 05:39:30 (65.116.131.6)
I'd suggest starting with the 100 or 80AZ amp - a lot fewer parts to deal with, few adjustments. I have a few Sams and Fisher manuals on my web page below: .......
416: Tube DIY Asylum, RE: 18A5 sound fine in triode mode ? (0.00)
Posted by Tom Bavis on 2011-08-10, 06:19:56 (65.116.131.6)
Not a common tube - I have a single used one, smoked glass, so I can't see the construction. I assume it's similar to 6AU5 - same size and pin connections. .......
417: Vintage Asylum, RE: Fisher 50az Schematics Request (0.00)
Posted by Tom Bavis on 2011-08-10, 06:15:46 (65.116.131.6)
Sams folder is on my web page: .......
418: Tubes Asylum, RE: 7591 sub.? (0.00)
Posted by Tom Bavis on 2011-08-04, 05:47:48 (65.116.131.6)
No and no. There ARE modern 7591s from EH and JJ, and there may still be some of the Sovtek 7591XYZ around (a repinned 6L6). The latter needed more negative bias (or added cathode resistor) to sub for .......
419: Tube DIY Asylum, RE: high voltage regulator IC from TI (0.00)
Posted by Tom Bavis on 2011-08-03, 05:28:49 (65.116.131.6)
Also look at the TL783- has a high-voltage MOSFET pass element. .......
420: Tubes Asylum, RE: Power Tube issue (0.00)
Posted by Tom Bavis on 2011-08-03, 05:22:40 (65.116.131.6)
Assuming id DID glow at the top before (not all do...), the heater element may have dropped down into the cathode tube. If it extends further out on the bottom, it's possible it could short to somethi .......
421: Tubes Asylum, RE: RCA 6C9: Anyone familiar? Yes! (0.00)
Posted by Tom Bavis on 2011-07-26, 07:31:47 (65.116.131.6)
I actually have at least one radio that uses it... but I have NOS and used ones already. And my Knight 600A will test it... .......
422: Tube DIY Asylum, RE: Does 12AZ7 = 12AT7 for CF duty? (0.00)
Posted by Tom Bavis on 2011-07-25, 06:55:42 (65.116.131.6)
I think the 12AZ7 was intended as a 12AT7 replacement with higher heater-cathode breakdown voltage. Maybe the extra insulation made a larger cathode surface area, requiring more heat for the same temp .......
423: Tubes Asylum, RE: 6ez5 replace 5881? (0.00)
Posted by Tom Bavis on 2011-07-08, 07:15:04 (65.116.131.6)
No - voltage rating is too low. It can replace 6V6, but will likely require bias (cathode resistor) change. .......
424: Tubes Asylum, RE: Amperex 12AX7 orange globe... (0.00)
Posted by Tom Bavis on 2011-06-17, 08:08:06 (65.116.131.6)
I have Amperex orange globe 12AX7s (also marked 7025) with the distinctive GE etched lettering, '75 (printed) date code. They're not "counterfeits" if they were labeled by Amperex... for that matter, .......
425: Tubes Asylum, RE: Need Fisher 290T schematic / docs + EL95 tubes (0.00)
Posted by Tom Bavis on 2011-06-05, 18:07:13 (69.205.116.106)
If the heater winding can take a little extra load, the 6AQ5 should work... might have to adjust the cathode resistor (haven't compared the curves...). .......
426: Vintage Asylum, RE: Kenwood "800" Tube Receiver (0.00)
Posted by Tom Bavis on 2011-05-10, 06:16:40 (65.116.131.6)
Looks a lot like the Lafayette LR-800. 7189 output tubes? I have that schematic at the bottom of my audio page... .......
427: Tubes Asylum, RE: Is there a 12A_7 tube that is around 30 in gain? (0.00)
Posted by Tom Bavis on 2011-05-02, 06:22:37 (65.116.131.6)
Mu is the maximum available "amplification factor" - the gain with a constant-current load (effectively infinite resistance). With typical circuit values, a 12AX7 delivers a gain of about 60. See the .......
428: Tube DIY Asylum, RE: Running 26.5V tubes at 24V (0.00)
Posted by Tom Bavis on 2011-04-25, 07:21:21 (65.116.131.6)
Parallel the plates within a tube - diodes are more likely to be matched, ESPECIALLY a few years from now when one needs to be replaced... also avoids having the full transformer voltage on a socket - .......
429: Vintage Asylum, RE: Fisher 80AZ zmatic (0.00)
Posted by Tom Bavis on 2011-04-20, 07:30:55 (65.116.131.6)
Quite possible that there's a oxide film on the switch contacts so that an ohmmeter won't make it conduct - wouldn't be a problem on a power switch, as 117V would instantly burn it away. Anyway, the g .......
430: Vintage Asylum, RE: Info needed on Motorola 52M3U radio (0.00)
Posted by Tom Bavis on 2011-04-19, 07:44:08 (65.116.131.6)
Sams folder is dated 1952 - the "52" in the model number may the year. I see it does have a 117V input as well as battery - so it would be usable without too much work. The schematic and parts list is .......
431: Tube DIY Asylum, RE: Surplus Choke Markings (0.00)
Posted by Tom Bavis on 2011-04-16, 10:29:54 (69.205.116.106)
10V is the test voltage (inductance will vary with applied voltage). .......
432: Tube DIY Asylum, RE: Help on Brocken 5lbs xfrmr problem? I can use some good ideas. (0.00)
Posted by Tom Bavis on 2011-04-15, 14:10:22 (65.116.131.6)
The transformer end bells can be replaced - either from a junk transformer for the same lamination size, or with new ones from Edcor (those require painting, though...) .......
433: Vintage Asylum, RE: Stromberg Carlson 713c console rebuild (0.00)
Posted by Tom Bavis on 2011-04-03, 08:25:45 (69.205.116.106)
You'll find it listed under the amplifier chassis on my site - ASR-110. I think I have the Sams folder for the turntable too - haven't scanned it yet. .......
434: Tube DIY Asylum, RE: PSUDII Heater Sim (0.00)
Posted by Tom Bavis on 2011-04-01, 13:51:27 (65.116.131.6)
Cold resistance will be a fraction of hot resistance, but you can measure it easily on any tube. Hot resistance is measured indirectly by V/I. And V/I is also the answer to the dropping resistor - you .......
435: Tube DIY Asylum, RE: Cornell-Dubilier Avionics Grade Capacitors - 50 year operating life! (0.00)
Posted by Tom Bavis on 2011-03-29, 06:04:46 (65.116.131.6)
2000 Hours at maximum temperature and ripple current. Double that for every 10 deg C drop in temperature. So if you're operating them at 35 deg C, expect more than 64,000 hours life... .......
436: Vintage Asylum, RE: Anyone want to take a crack at a 1948 Magnavox FM tuner? (0.00)
Posted by Tom Bavis on 2011-03-24, 05:35:38 (65.116.131.6)
Chassis number? (CR-xxx) Probably covered in Sams, maybe in Riders: .......
437: Vintage Asylum, RE: I just bought this amp for 145. (0.00)
Posted by Tom Bavis on 2011-03-22, 11:38:02 (65.116.131.6)
RMA is the Radio Manufacturer's Association - later to become the EIA. Code number 238 is Thordarson-Meissner. Riders doesn't seem to have any Meissner information, but Sams does list a few, including .......
438: Tube DIY Asylum, RE: AC/DC (0.00)
Posted by Tom Bavis on 2011-03-15, 16:20:57 (74.69.101.247)
Doubler will lose two diode drops (about a volt) from 12.6V or about 8%. A full-wave bridge will lose two diode drops (slightly more due to higher current) from 6.3V or about 18%. So the doubler makes .......
439: Vintage Asylum, RE: Fisher Allegro Update (0.00)
Posted by Tom Bavis on 2011-03-15, 16:10:36 (74.69.101.247)
You can find a schematic for the similar X-190 in the database at audiokarma.org. .......
440: Tube DIY Asylum, RE: Negative Supply (0.00)
Posted by Tom Bavis on 2011-03-03, 06:28:16 (65.116.131.6)
If you want the grid at 0V (to eliminate the input coupling cap), you need a negative supply. If you use a large tail resistor, you'll need more B+ voltage to get the same operating point. ::: TOPIC:: .......
441: Vintage Asylum, RE: Fisher Allegro ELL80 Reco's.. (0.00)
Posted by Tom Bavis on 2011-03-03, 06:17:49 (65.116.131.6)
You rang? As a matter of fact, I think I DO have that schematic - email me and I'll send it tonight. tbavis(at)rochester(dot)rr(dot)com .......
442: Tube DIY Asylum, RE: Transformer/Voltage Doubler/Damper Diode Questions (0.00)
Posted by Tom Bavis on 2011-02-09, 06:24:49 (65.116.131.6)
I did a quick PSUD simulation and found 725 mA in the transformer with 140 mA DC from the doubler. -BUT- The 0.7A rating may be conservative - measure the winding resistance. And you're not using the .......
443: Tube DIY Asylum, RE: Somebody please help me with basic dumpster choke selection tech. (0.00)
Posted by Tom Bavis on 2011-01-13, 19:38:32 (74.69.101.247)
No, it means you might not measure the rated inductance if you measure it at conditions other than 10V and 60 Hz. Inductance varies with applied AC voltage, DC current, and test frequency. Given the s .......
444: Tube DIY Asylum, RE: Acceptable DC through coupling cap (0.00)
Posted by Tom Bavis on 2011-01-13, 19:29:21 (74.69.101.247)
I would change the cap if the .5V is present with 300B removed - leakage isn't linear with voltage and it increases with temperature... but it COULD be grid leakage on the 300B. Not enough to affect b .......
445: Tube DIY Asylum, RE: Somebody please help me with basic dumpster choke selection tech. (0.00)
Posted by Tom Bavis on 2011-01-12, 10:37:38 (65.116.131.6)
"10V 60 cycles" defines the conditions for measuring the inductance. It will vary depending on test frequency and voltage. .......
446: Tubes Asylum, RE: Clear top (not necc RCA) 12SN7s? (0.00)
Posted by Tom Bavis on 2011-01-07, 20:09:53 (74.69.101.247)
How about the "hot wire" GEs? The have a top connection between the sections that glows. I think that any I have are 6SN7 though. .......
447: Tube DIY Asylum, RE: Looking for tube similar to 6CG7 but with Vhk rating )300 (0.00)
Posted by Tom Bavis on 2010-12-27, 12:50:34 (65.116.131.6)
6900. Not pin compatible, of course, and you might have to sell your car to get a few... .......
448: Tubes Asylum, RE: Scott 222d 6U8/6GH8/E80CF (0.00)
Posted by Tom Bavis on 2010-12-07, 08:14:45 (65.116.131.6)
Always check voltages when you replace one of these... much of the difference in sound will be due to a change in operating point, since it's a direct-coupled stage. Dynaco ST-70s are bad enough, and .......
449: Tubes Asylum, RE: Consider Webcor (Mullard) 7025 (12AX7) (0.00)
Posted by Tom Bavis on 2010-12-03, 08:55:57 (65.116.131.6)
In most cases, there is no difference in the tubes that are labeled with a different name - a few OEMs may have had tighter specs that required selection... but extra testing adds cost. The Mullards m .......
450: Tube DIY Asylum, RE: Change EL86 to EL84 or to 6N14N-EB (0.00)
Posted by Tom Bavis on 2010-11-18, 06:25:00 (65.116.131.6)
EL84s will probably give less power... the transformer is likely 4K, not 8K or higher. You can get a little more power by using a common cathode resistor (half the value) for both tubes - but they mus .......
451: Tube DIY Asylum, RE: Possible Rectifier Solution? (0.00)
Posted by Tom Bavis on 2010-11-15, 08:28:20 (65.116.131.6)
6AX5 can do 125 mA - downside is that it needs 1.2A for the heater. .......
452: Tubes Asylum, RE: 6RR8C Tubes (0.00)
Posted by Tom Bavis on 2010-11-12, 13:16:42 (65.116.131.6)
These seem to be the equivalent of 404A / 5847. .......
453: Tubes Asylum, RE: Mullard ECC83 Square Halo code ? (0.00)
Posted by Tom Bavis on 2010-10-22, 07:23:02 (65.116.131.6)
1022 is the EIA code for IEC electronics, the US importer for Mullard. 736 is 1957, week 36. .......
454: Tubes Asylum, RE: 6SQ7 vs. 6SF5 (0.00)
Posted by Tom Bavis on 2010-10-22, 07:20:20 (65.116.131.6)
Right - 6SQ7 was made in much more volume than 6SF5, so it may have been cheaper and was certainly more readily variable. Almost every transformer operated radio used the 6SQ7 as detector and first au .......
455: Tube DIY Asylum, RE: First project - old audioXpress article. (0.00)
Posted by Tom Bavis on 2010-10-18, 10:31:45 (65.116.131.6)
I'd use 130LA10 or equivalent on 120V, 250LA10 on 240. Panasonic, Siemens make equivalents, I'm sure there are more. $20 shipping from Mouser? I'm sure they could send it First Class if asked... ::: .......
456: Tubes Asylum, RE: Tube testing settings for Knight 600 tester (0.00)
Posted by Tom Bavis on 2010-10-18, 05:49:41 (65.116.131.6)
They're on the roll chart... along with the most common tubes. If your doesn't have one, I'll see what I can come up with - tbavis(at)rochester(dot)rr(dot)com .......
457: Tube DIY Asylum, RE: A fuse riddle that I am trying to solve (0.00)
Posted by Tom Bavis on 2010-10-17, 07:37:32 (74.69.101.247)
I assume it's 50 Hz? Inrush current will be higher than 60 Hz. A thermistor or slow-blow fuse may be needed that would not be required on 60 Hz. But BE SURE the transformer is rated for use on 50 Hz! .......
458: Vintage Asylum, RE: How do I adapt guillotine jack to banana jack (female) (0.00)
Posted by Tom Bavis on 2010-10-15, 17:20:53 (74.69.101.247)
If .080" "phone tip" pins wlll fit, there are numerous adapters available - DigiKey has a package of ten for $13.50. Google "banana to pin adapter" .......
459: Tube DIY Asylum, RE: Common Power Supply For Stereo (0.00)
Posted by Tom Bavis on 2010-10-15, 13:55:13 (65.116.131.6)
You need a power transformer with twice the current rating, and if a choke was used, it can be half the value but twice the current rating. Better would be two chokes, one per channel. Feedback resist .......
460: Tube DIY Asylum, RE: secodary filament amperage (0.00)
Posted by Tom Bavis on 2010-10-09, 05:31:02 (74.69.101.247)
There are other factors to consider besides current density in secondary wire. First is maximum copper loss - a transformer design may be close to maximum loss, so one winding is changed to reduce it .......
461: Vintage Asylum, RE: A thing of beauty (0.00)
Posted by Tom Bavis on 2010-10-08, 18:34:43 (74.69.101.247)
Yes, you stole it. If you don't have a copy, the Sams folder is on my web page: http://www.audiophool.cjb.net/MadeInRoch.html I have his 6V6 based little brother, SR-407. .......
462: Tubes Asylum, RE: Tube Life- Power Cycling (0.00)
Posted by Tom Bavis on 2010-10-04, 13:10:31 (65.116.131.6)
Some power tubes will have less than 2000 hours of life when operated at maximum ratings. Life increases dramatically when they're operated more conservatively. And some small signal tubes (which are .......
463: Tube DIY Asylum, RE: Shock Hazard (0.00)
Posted by Tom Bavis on 2010-09-24, 07:42:59 (65.116.131.6)
A .01 uF capacitor will pass 0.8 mA at 250V, 50 Hz, much less at 117V, 60 Hz. Transformer leakage will much less than this if the insulation is good - capacitance of a few hundred pF at most. The "sta .......
464: Tubes Asylum, RE: Ok (0.00)
Posted by Tom Bavis on 2010-09-24, 07:32:21 (65.116.131.6)
A 12AX7 will test like a weak 12AU7... .......
465: Tubes Asylum, RE: Is there a current production 12BZ7 tube??? (0.00)
Posted by Tom Bavis on 2010-09-23, 17:03:11 (74.69.101.247)
They're generally quite microphonic with the extra long plate and grid structure. May be OK in later stages, not so good in front end. .......
466: Tubes Asylum, RE: Triode Mode cause amp to run hotter? (0.00)
Posted by Tom Bavis on 2010-09-20, 07:32:31 (65.116.131.6)
Idle current will be SLIGHTLY lower, since screen will have a little more voltage drop in the transformer - other than that, the DC operating point (and dissipation) is the same. .......
467: Vintage Asylum, RE: Slightly hot chassis (0.00)
Posted by Tom Bavis on 2010-08-31, 07:34:49 (65.116.131.6)
No, line-to-chassis capacitors do this - they MIGHT be leaky, but even if not they can pass some current to the chassis. Flip the AC plug, may go away. Even better, find 'em and replace with a modern .......
468: Tube DIY Asylum, RE: Current Source Filaments (0.00)
Posted by Tom Bavis on 2010-08-23, 06:33:40 (65.116.131.6)
If you just have a single 12V tube, a voltage doubler (using Schottky diodes) may be all you need. .......
469: Tubes Asylum, RE: My B&K 707 sensitivity seems wonky (0.00)
Posted by Tom Bavis on 2010-08-23, 06:29:45 (65.116.131.6)
Also clean the contacts on the two bulbs (#55) in the grid signal circuit - I have heard some recommend SOLDERING these into the circuit. .......
470: Tubes Asylum, RE: MICROPHONICS (0.00)
Posted by Tom Bavis on 2010-08-17, 12:05:53 (65.116.131.6)
There's a chapter in Tomer's "Getting the Most from Vacuum Tubes" (1960) covering "Noise, Microphonics and Hum". Find it on Pete Millett's site. Likewise, F. Langford Smith mentions using a "non-micro .......
471: Tubes Asylum, RE: Arcturus 12BH7....thumbs up or down? (0.00)
Posted by Tom Bavis on 2010-08-11, 05:52:41 (65.116.131.6)
The Arcturus name was exhumed in the '50s as a re-brander - no longer a manufacturer. You may be able to ID the actual maker by internals. .......
472: Tubes Asylum, RE: Substitutes for 6N1P (0.00)
Posted by Tom Bavis on 2010-08-04, 06:11:54 (65.116.131.6)
6BK7 and 6BQ7 are probably closest - I'm not sure that they're as linear as the 6N1P - but it won't cost much to try 'em... about $5 each for NOS. 6DJ8, 6922 etc. MIGHT require some resistor value ch .......
473: Tubes Asylum, RE: new tubes (0.00)
Posted by Tom Bavis on 2010-07-26, 08:51:49 (65.116.131.6)
12AX7s should last through a couple of sets of power tubes - 12AT7 would possible not last as long, depending on circuit. Clean the pins and sockets - usually a bigger problem than the tubes themselve .......
474: Tube DIY Asylum, RE: RCA 5691 / 5692 (0.00)
Posted by Tom Bavis on 2010-07-25, 17:08:47 (74.69.101.247)
Breathe heavily on the glass, above the octal keyway (that's where RCA usually put it). You might see a faint number... .......
475: Tube DIY Asylum, RE: Ampex 620 - good El Cheapo donor? (0.00)
Posted by Tom Bavis on 2010-07-20, 08:07:57 (65.116.131.6)
I would not strip the 620s as I think they're worth more than the parts... I'd sell them which would more than finance a DIY project... .......
476: Tubes Asylum, RE: Stromberg Carlson tubes (0.00)
Posted by Tom Bavis on 2010-07-15, 11:46:10 (65.116.131.6)
Agree with Jim: could be any maker. I have a sample of 1 pair... Tung-Sol, code 322. 312 is Sylvania, 274 RCA, 188 is GE. .......
477: Tubes Asylum, RE: Mike,it has the settings. (0.00)
Posted by Tom Bavis on 2010-07-14, 14:17:53 (65.116.131.6)
No, the 6BM8 and 6GW8 are different in pinout and ratings, though they're both hi-mu triode, power pentode. Look also for ELL80 and ECL86 which are the Euro numbers. My Knight 600 has data for 'em - I .......
478: Tube DIY Asylum, RE: Generating Negative Voltage from a single Taping on transformer (0.00)
Posted by Tom Bavis on 2010-07-09, 05:47:25 (65.116.131.6)
Add a capacitor in series with the diode - that'll work with FWB. A shunt resistor is needed as a load to carry the positive current (negative is through diode). Actual values will need simulation or .......
479: Vintage Asylum, RE: Bogen SRB-20 (0.00)
Posted by Tom Bavis on 2010-07-09, 05:41:02 (65.116.131.6)
Sams Photofact folder 514-7 covers it - 1961. Not in my files, though. $7 for a scan from Sams website, but first ask at your library - some can get you them for the cost of the copies. .......
480: Vintage Asylum, RE: Bogen D10 (0.00)
Posted by Tom Bavis on 2010-07-08, 18:52:56 (74.69.101.247)
Schematic is online at the link below: .......
481: Vintage Asylum, RE: Anyone in the Syracuse, NY Area? (0.00)
Posted by Tom Bavis on 2010-07-04, 10:04:10 (74.69.101.247)
I live in Macedon - maybe 70 miles away... .......
482: Vintage Asylum, RE: AMPEX 954 (0.00)
Posted by Tom Bavis on 2010-06-24, 05:47:47 (65.116.131.6)
Service data is in Sams folder 452-5. I don't think I have it though... .......
483: Tube DIY Asylum, RE: My 30 dollar ham fest finds today. (0.00)
Posted by Tom Bavis on 2010-06-19, 20:12:11 (74.69.101.247)
Maybe a Taylor T-21? Pretty much a 6L6 in a 6-pin base, like 42 or 2A5. I should show the $10 box of tubes I hauled home from the Rochester hamfest... 4-5881s, 8-45s, 3-71As, five Arcturus blues... e .......
484: Vintage Asylum, RE: Take a look at this Scott guys (0.00)
Posted by Tom Bavis on 2010-06-18, 09:00:36 (65.116.131.6)
Clean the controls and replace a few caps, replace any weak tubes and it'll be ready for its next 50 years... Mine shows ZERO leakage on the coupling caps but they used several kinds of caps during it .......
485: Tubes Asylum, RE: What is this "tube"??? (0.00)
Posted by Tom Bavis on 2010-06-17, 07:34:35 (65.116.131.6)
It's the original version of the 5Z4 - later replaced by glass and conventional metal versions. I believe there are two exposed anodes inside, each an evacuated shell with cathode inside. .......
486: Vintage Asylum, RE: Take a look at this Scott guys (0.00)
Posted by Tom Bavis on 2010-06-17, 06:43:38 (65.116.131.6)
Not REALLY E.H. Scott - but Scott Radio Company was a successor to the great '1930s company. H.H. Scott sued them and WON to prevent them from using the Scott name. This IS an ASR-433 amp with a diffe .......
487: Tube DIY Asylum, RE: breadboard sockets (0.00)
Posted by Tom Bavis on 2010-06-07, 07:20:51 (65.116.131.6)
The ones below have turret terminals - if you have the space, you can use for permanent construction too... .......
488: Tube DIY Asylum, RE: Please explain - output tubes with big heater-cathode leakage (0.00)
Posted by Tom Bavis on 2010-05-30, 10:08:47 (74.69.101.247)
Output tubes with heater-cathode leakage aren't likely to be a problem. SHORTS, on the other hand, ARE a problem. But even a shorted one could be used if the heater supply is floating. .......
489: Tube DIY Asylum, RE: Sign of poor quality control or design ? (0.00)
Posted by Tom Bavis on 2010-05-22, 19:37:31 (74.69.101.247)
Insert shorting plugs into your unused inputs and the crosstalk will be gone. But who cares what happens on an UNUSED input? My TV makes funny noises when I put it between channels... .......
490: Vintage Asylum, RE: Fisher FM 50-B (0.00)
Posted by Tom Bavis on 2010-05-21, 05:40:59 (65.116.131.6)
I don't know how a selenium can have five terminals - check with an ohmmeter - two may be the same terminal. As for schematic, can't help. But Sams index shows "#889 - See contents" for FM-50B. Doesn' .......
491: Vintage Asylum, RE: Need help in replacing receiver dial bulb with correct one (0.00)
Posted by Tom Bavis on 2010-05-20, 05:44:02 (65.116.131.6)
Parts Express has 8V 0.25A bulbs - close enough to 0.3A (300 mA) .......
492: Tube DIY Asylum, RE: choke ratings question (0.00)
Posted by Tom Bavis on 2010-05-20, 05:39:03 (65.116.131.6)
Since .05H will be only 18 Ohms at 60 Hz, the function generator may not be able to drive it to the saturation voltage - you'll need an amplifier. Connect it through a resistor (maybe 10-47 Ohms) - in .......
493: Tube DIY Asylum, RE: choke ratings question (0.00)
Posted by Tom Bavis on 2010-05-19, 08:05:10 (65.116.131.6)
Those ratings are how it's measured. How it can be USED is another matter entirely. Are they as large as a commercial part of similar inductance and current ratings? If so, they'll probably work for y .......
494: Tubes Asylum, RE: 6AN8 Variety (0.00)
Posted by Tom Bavis on 2010-05-17, 05:34:49 (65.116.131.6)
I have some IEC Mullard 6AN8s... check the codes printed at the bottom of the tube - a Mullard will have a code starting with "B" or "R". .......
495: Tube DIY Asylum, RE: doubler vs FWB low resistance PS (0.00)
Posted by Tom Bavis on 2010-05-07, 19:20:37 (74.69.101.247)
Your doubler transformer has a lower VA rating - it will be 1/4 of the resistance of a 450V winding or 1/16 the resistance of a 450-0-450 winding to be equivalent in VA capacity. And for electrolytics .......
496: Tube DIY Asylum, RE: 1959 Ampex 6973 Monoblocks (0.00)
Posted by Tom Bavis on 2010-04-29, 05:30:13 (65.116.131.6)
6CZ5 is the closet equivalent if you can't come up with enough 6973s - but there are NEW ones from EH. I have a schematic - tbavis(at)rochester(dot)rr(dot)com Basic Mullard circuit. .......
497: Tube DIY Asylum, RE: Hybrid bridge rectifier (0.00)
Posted by Tom Bavis on 2010-04-28, 05:48:05 (65.116.131.6)
Cathodes connect to the (+) output, so you can run 'em in series or parallel on the same heater winding. .......
498: Vintage Asylum, RE: Anyone try 6BL8 as a driver in ST70? (0.00)
Posted by Tom Bavis on 2010-04-27, 05:51:27 (65.116.131.6)
Same pinout as 6GH8, though you might have to tweak the screen resistor for the best operating point (you may have to do that with 7199s too...) .......
499: Tubes Asylum, RE: Tube Tester Variation Question Again . . . (0.00)
Posted by Tom Bavis on 2010-04-23, 06:03:44 (65.116.131.6)
What do other 7591s read on your tester? Transconductance varies greatly with the operating point. And every tube tester data chart has errors, some minor, some ridiculously large. .......
500: Tube DIY Asylum, RE: Would OT and PT trannys for 12AB5s work for (0.00)
Posted by Tom Bavis on 2010-04-09, 05:23:57 (65.116.131.6)
They should be 5-6K - 12AB5 is similar to 6V6. .......
Found total of 500 records, Query: , Author: Tom Bavis in All Forums, Time: 1 sec.